Search

Interspecific aggression is common in birds—Individuals regularly chase and attack members of other species. We analyzed cases of interspecific aggression between crows (American Crow [Corvus brachyrhynchos] and Northwestern Crow [C. caurinus]) and ravens (Common Raven [C. corax]) using ∼2,000 citizen scientist observations of interspecific aggression between crows and ravens from across North America. Crows and ravens may attack one another for nonadaptive reasons, because they compete with each other for food and space, or because they are nest predators of each other. We report 3 main results. First, although ravens are much larger than crows, crows chased and attacked ravens in ∼97% of observations. We observed this strong asymmetry in the direction of interspecific aggression throughout North America. Second, crow aggression toward ravens was most frequent during the crows' nesting season (∼March–May), but also occurred in other seasons. Third, crows typically attacked ravens in small groups...

Intensive agriculture, as is typical of corn and soybean production, may be responsible for declines in the abundance and diversity of farmland birds. In Quebec, the transition to intensive crops is evidenced by marked increases of corn and soybean fields. From 2008 to 2010, we used satellite telemetry to study use of corn (Zea mays) and soybean (Glycine max) fields, other farmlands, wetlands, urban areas, and other habitats by 10 female Peregrine Falcons (Falco peregrinus) of the anatum—tundrius complex, a taxon of “special concern” in Canada. We monitored females during the nesting season, from hatching of eggs to independence of young, but before the young dispersed away from the nest site. Adult females were less likely to use corn and soybean fields than the “other farmlands” and “other habitats” categories during the nestling stage and the first month after young fledged. Once young fledged, other farmlands and urban areas were more likely to be used than the “other habitats” category when...

Studies of reproduction and habitat use are essential for any species assessment, especially for species with declining populations. We compared habitat in nest sites and randomly selected sites within Golden-winged Warbler (Vermivora chrysoptera) territories. We also modeled the effects of temporal and biotic factors on daily nest survival in relation to the constant-survival model. The percent cover of herbaceous vegetation was greater at nest sites, and that of woody vegetation was greater at non-nest sites. There was support for models with annual variation and a decline in nest survival throughout the nesting season, but the constant-survival model performed equally well. One parameter performed marginally better than the constant-survival model: nests with a woody stem in the substrate had lower nest-survival rates. We conclude that nest-site selection was nonrandom, such that females use specific criteria to select nest sites. However, habitat characteristics did not appear to significantl...

In hay fields in the northeastern United States, Savannah Sparrows (Passerculus sandwichensis) whose first nests fail as a result of the harvesting of hay renest in the same field in a dramatically altered habitat. We evaluated availability of invertebrate prey in two treatments (harvested and unharvested hay fields) in Vermont's Champlain Valley and assessed potential effects of food resources on clutch size, food provisioning by adults, and growth of nestling Savannah Sparrows. A relative measure of invertebrate biomass (sweep-net samples) showed a 36–82% decline after harvesting, compared with continual increases throughout the nesting season on unharvested fields. Clutch sizes were not significantly different between treatments. Nestling provisioning rates obtained through video observations differed between treatments, with birds on unharvested fields delivering 73% more food than those on harvested fields (P = 0.02). However, food provisioning differences did not translate into differences ...

During at least one of three nesting seasons, 13 breeding pairs of Crested Caracaras (Caracara plancus) in south-central Florida made a second nesting attempt following a successful first attempt. Ten pairs successfully fledged young in both attempts. Only early nesting pairs attempted a second brood. Most double-brooded pairs fledged their first brood before 1 March. The time interval between first and second nesting attempts was positively correlated with the number of young fledged from the first attempt. Clutch size declined between first and second nests of double-brooded pairs, and second nests failed more often, but pairs that attempted two broods in a season fledged significantly more young than did single-brooded pairs. Estimates of survivorship to recruitment were higher for young from first broods than for young from single or second broods. Although the influence of double brooding on annual productivity seems only marginal, this strategy likely persists because of the potential increase in fitness incurred by individuals that successfully fledge two sets of young in a single nesting season. Received 24 February 1997, accepted 19 March

AISTICT.--Florida Scrub-Jay (Aphelocoma coerulescens) demography and cooperative breed- ing were measured from 1988 to 1993 at two sites (HC and T4) on John F. Kennedy Space Center along Florida's Atlantic coast. The results from HC and T4 sites were compared with published results from the Archbold Biological Station in central Florida. The T4 population increased because of reproductive success and immigration, resulting in a nearly equal non- breeder sex ratio. Nearly all young Florida Scrub-Jays delayed breeding for at least two years after hatching at T4, similar to Archbold. The HC population decreased because of poor nesting success, and the nonbreeder sex ratio was biased towards males. During the first nesting season after hatching, nearly one of every five HC females bred. Pairs with non- breeders (potential helpers) usually had greater reproductive success than pairs without nonbreeders at HC and Archbold, but not T4. Pairs with nonbreeders usually had greater survival than pairs without nonbreeders at Archbold, but not at HC or T4. Female breeder mortality was slightly higher than male breeder mortality at T4 and HC, but not at Archbold. Evidence suggested that predation contributed to differences in demographic patterns be- tween study areas. Received 3 fuly 1995, accepted 21 September 1995. MOST STUDIES on the Florida Scrub-Jay (Aphel- ocoma coerulescens) are from oak-dominated scrub at Archbold Biological Station (Archbold), where optimal habitat is excessively drained, contains many open sandy areas, and has few trees (Woolfenden and Fitzpatrick 1984, 1991). One of the largest contiguous populations of the fed- erally threatened Florida Scrub-Jay occurs on John F. Kennedy Space Center (KSC; Cox 1987). Most KSC habitat is composed of patches of scrub oaks in a matrix of poorly drained flat- woods vegetation and marshes (Breininger et al. 1991, 1995). Because of alterations of the nat- ural fire regime, most KSC habitat has taller vegetation and fewer openings than optimal Archbold scrub (Breininger 1981; Breininger and Schmalzer 1990; Schmalzer and Hinkle 1992a, b). Florida Scrub-Jays inhabit all-purpose terri- tories defended year-round by a permanently monogamous breeding pair (Woolfenden and Fitzpatrick 1984, Breininger et al. 1995). Except where subject to habitat loss and fragmentation, most Florida Scrub-Jays disperse short distances (one to three territory widths) and occupy a territory for life after becoming breeders. Young Florida Scrub-Jays usually remain as nonbreed- ers (potential helpers) with the breeders for at

The timing and production of crop milk are important to the reproductive tactics of granivorous columbids, but little is known about crop-milk production in frugiv- orous columbids. We examined the diet of nestling White-crowned Pigeons (Columba leuco- cephala) and the relative contributions of crop milk and fruit during different stages of nestling development. The diet was dominated by five species of plants: Metopium toxiferum (poison- wood), Guapira discolor (blolly), Ficus citrifolia (shortleaf fig), F. aurea (strangler fig), and Erithalis fruticosa (black torch). Fruit of F. aurea and F. citrifolia dominated the diet during May and June. Fruit of M. toxiferum, which began to ripen in early July, dominated the diet through September. Guapira discolor was found in the diet throughout the nesting season and, overall, ranked as the second-most-important food. Erithalis fruticosa was found in small amounts in samples collected throughout the season. Crop milk remained an important component of the diet throughout the nestling period. As nestlings grew, fruit was added to the diet. At ages 0 to 2 days, the diet was entirely crop milk. The proportion of the diet composed of fruit increased from 10% on day 3 to 65% at day 15. These data suggest that the reproductive tactics of frugivorous pigeons may differ from those of granivorous pigeons. We speculate that frugivorous columbids may continue to supplement the diet of nestlings and fledglings with crop milk. Although this behavior may enhance growth rates and survival of individual young, it also may lengthen the interclutch interval. These findings emphasize the conser- vation importance of protecting large feeding areas to maintain populations of threatened and endangered frugivorous pigeons. Received 8 June 1992, accepted 15 March 1993. THE WHITE-CROWNED PIGEON (Columba leuco- cephala) nests throughout most of the Caribbe- an, in the Florida Keys, and along the Central American coast of the Caribbean (Arendt et al. 1979, AOU 1983, Strong et al. 1991). In Florida, White-crowned Pigeons nest from May through September on small mangrove islands in and around Florida Bay, but forage in the hardwood forests of the mainline Florida Keys (Strong et al. 1991), where they feed exclusively on fruits of hardwood trees (Wiley and Wiley 1979). These hardwood forests have been extensively cleared (Strong and Bancroft 1994a), thus threatening this pigeon species (Bancroft in press, Strong and Bancroft 1994b). The Florida Game and Freshwater Fish Commission has listed the White-crowned Pigeon as Threatened (Wood 1990). Understanding their food requirements

Encounter-sampling designs are data-collection procedures in which population units are included in the sample as they are detected, or "encountered." Perhaps the most familiar examples of encountersampling designs are line-transect (e.g. Burnham et al. 1980) and line-intercept (e.g. De Vries 1979) procedures. One characteristic of encounter-sampling designs is that a sampling frame (e.g. Cochran 1977) of population units is not required. When individuals are mobile, elusive, or possess other characteristics that make it difficult to construct a sampling frame, encounter-sampling designs often provide the only effective means of sampling a population. A second characteristic of encounter-sampling designs is that they lack control over the subset of the population comprising the sample. As a result, data collected by these procedures often are not representative of the population of interest (i.e. a biased sample), and are best viewed as a probability sample. If variables of interest are correlated with the probability of inclusion, the data cannot be treated as a simple random sample, and estimators based upon random sampling theory are biased (Rao 1965). In these cases, designspecific estimators or bias corrections dependent on the probability structure of the data must be employed. A population of bird nests is one example of a population whose study requires the use of an encountersampling technique. In addition to the obvious lack of a sampling frame, the population is demographically open in that nests are initiated and fail through time. The usual sampling design consists of conducting searches for viable nests, including all detected nests in the sample. Data collected under such a design are biased because longer-lived nests are included in the sample with higher probability than are shorter-lived nests (Mayfield 1961). However, the method by which searches are conducted, typically, is not structured and is not helpful in deriving estimators. The parameter most often of interest is the nestsurvival rate (i.e. probability a nest survives to "success"). Success is often defined as the production of at least one offspring, though other definitions are equally appropriate. Nest-survival rates may be estimated using a number of models. Mayfield (1961, 1975), Johnson (1979), and Bart and Robson (1982) modeled nest survival after detection. Hensler and Nichols (1981), Pollock and Cornelius (1988), and Bromaghin and McDonald (1993) modeled the entire existence of nests by incorporating probabilities of inclusion and partial information of the total lifetime of detected nests in the model. While all of these models attempt to treat the probability structure of the data, only the Pollock-Cornelius and BromaghinMcDonald models do so fully and correctly. Although Heisey and Nordheim (1990) indicated that the Pollock-Cornelius model produces biased estimates of nest survival, recent information (Pollock and Cornelius unpubl. data) suggests that the bias decreases as the time between visits to nests decreases. All of the nest-survival models are designed to produce estimators of a single parameter, the probability of nest-success, while acknowledging the biased nature of the data. To some extent, they have all been successful. However, any number of additional parameters may also be of interest, and their estimation, which is also complicated by the biased nature of the data, has received little attention. We present a sampling design and estimation procedures that directly utilize the unequal probabilities with which nests are included in the sample. The method is developed from a classical sampling approach in that all characteristics of the population of nests are considered as fixed; randomness observed in the data is due solely to the sampling design. The design consists of temporally systematic searches for nests, and nests are included in the sample as they are detected. The model assumes that nests are (approximately) aged at the time of detection and monitored until they either fail or are successful. The systematic design permits probabilities of inclusion to be estimated. The estimates are employed in modified Horvitz-Thompson estimators (Horvitz and Thompson 1952) to obtain estimates of any parameter that can be expressed as a total or a ratio of totals. Such parameters include the probability a nest survives to success, the number of nests which survive to success, and the numbers of nests initiated. The sampling model.-Consider a fixed geographic area in which birds are nesting. Nests are initiated and survive for some period of time. The population of interest consists of all nests which exist within the area for any portion of a specified time frame. For example, the time frame might be constructed to contain all or some interesting portion of the nesting season of the species under consideration. Thus, a geographic area and a time frame are used to define the population. The population size is denoted N and the number of time units in the time frame of interest is denoted D. The time frame of D time units is divided into a

In a population of Green Woodhoopoes (Phoeniculus purpureus) in the Rift Valley of Kenya, food abundance and breeding success varied greatly as a result of highly unpredictable patterns and abundance of rainfall. A given pair of woodhoopoes may breed successfully from zero to three times between May and December. We found a female-biased sex ratio in first nests of the year among those female breeders that had few (0-2) helpers. Apart from predation of entire broods, nestling mortality was extremely low (5%), and the bias was not based on differential starvation of male and female chicks. We examined several possible explanations for the female-biased sex ratio, and we suggest that production of female offspring by breeders in small groups is adaptive in that females are smaller and probably less expensive to rear than males. Young female nest helpers contributed significantly more feedings to subsequent broods than did their male siblings of the same age. The bias toward daughters could be effected either via nonrandom segregation of sex chromosomes or by differential mortality of eggs by sex. In several other bird species, larger eggs may give rise to males. This provides a possible means for the female parent to discriminate the sex of offspring before hatching. Received 23 January 1990, accepted 12 May 1990. IN ANIMALS that reproduce sexually, each breeding individual should attempt to maximize its lifetime reproduction. One way parents might enhance their own reproductive advantage is through facultative control of the sex of their offspring. For vertebrates, this is a controversial and poorly understood subject. Although numerous explanations exist for why individuals should control the sex of offspring under specific conditions (Trivers and Willard 1973, Myers 1978, Williams 1979, Burley 1982, Charnov 1982, Clutton-Brock and Albon 1982, Clutton-Brock 1986), evidence for adaptive control of offspring gender in birds is scanty (Howe 1977, Williams 1979, Fiala 1981, Richter 1983, Clutton-Brock 1986, Breitwisch 1989) and usually ambiguous (cf. Ankney 1982 and Cooke and Harmsen 1983, and Blank and Nolan 1983 and Weatherhead 1985). In his review of sex ratio variation in birds, Clutton-Brock (1986: 326) concluded that "Sound evidence for sex ratio variation at hatching is thus scarce." We report data that imply that in a cooperatively breeding bird (the Green Woodhoopoe, Phoeniculus purpureus), a female-biased sex ratio at hatching may occur under certain ecological and social conditions. METHODS AND PERTINENT NATURAL HISTORY We studied the social behavior and ecology of a marked population of Green Woodhoopoes near Lake Naivasha, Kenya, from mid-1975 through January 1982, and in June-July 1984 (Ligon and Ligon 1978, 1983, 1988, 1989a, b). Briefly, social units consist of 2-16 birds that contain no more than a single breeding pair, regardless of flock size. Each group defends a territory year-round, and territory size often is related positively to group size. In each year breeding normally begins in late May or early June, following the "long rains" of March to May, and generally terminates in December or earlier. The number of successful nesting efforts per year appears to be controlled by food availability, which in turn is determined largely by patterns of rainfall. Two broods during the period June to December are common, and if environmental conditions are extremely favorable, three broods can be produced by one pair during this interval. When conditions are poor, breeding activity is limited, and only one or even no nesting attempt may occur. In such years, there is a lot of territory-to-territory variation both in the time of breeding and in the number of nests attempted. Moth larvae make up the vast majority of food items of nestlings and adults during the sixor seven-month nesting season (unpubl. data), and numbers of these caterpillars through the year are related most directly to the amount of precipitation during the putative dry season, January to March. During this period, the moth caterpillars pupate in the ground and survive well only if the soil remains dry. If extensive rain falls during the "dry" season, mortality of the pupae is high, and few adults emerge to give rise to the generation of caterpillars that appears following the long rains. There is a significant inverse relationship between dry-season rainfall and subsequent repro765 The Auk 107: 765-771. October 1990 This content downloaded from 157.55.39.104 on Mon, 20 Jun 2016 06:37:42 UTC All use subject to http://about.jstor.org/terms 766 LIGON AND LIGON [Auk, Vol. 107 ductive success in this population of woodhoopoes (Ligon and Ligon 1989a, b). Nests are placed in tree cavities. We used an adjustable mirror and flashlight to inspect nest cavities after the eggs were laid. After determining clutch size, we generally did not inspect the nest again until the young began to hatch. This was indicated by changes in the behavior of the breeding female and helpers. After one or more eggs had hatched, the breeding female continued to eat large food items brought to her, but carried very small items into the nest cavity. As the eggs hatched, the helpers increased greatly the frequency of feeding visits and the number of minute food items brought to the nest. Unhatched eggs remained in the nest. Clutch size in Green Woodhoopoes varied little; 88% were either threeor four-egg clutches. Despite this conservatism in clutch size variation, one third of the eggs in clutches of all sizes failed to hatch (see Ligon and Ligon 1988: table V). Separation of the data by year revealed a similar pattern: one third of all eggs laid in each year did not hatch (Ligon and Ligon 1988: table VI). Ligon and Ligon (1988) attribute this high rate of hatching failure to inbreeding depres

The American Woodcock (Scolopax minor) is one of the earliest ground-nesting birds in the northeastern United States. In Maine, nesting begins in early April when temperatures can drop below freezing and significant snowfall can accumulate. Nests are usually in open woods, where eggs are laid on the ground in a shallow depression (Pettingill 1936, Mendall and Aldous 1943, Sheldon 1967). Peak hatching occurs in early May (Dwyer et al. 1982), when temperatures are cool and precipitation is common. Woodcock chicks are dependent on the female for most of their food for at least seven days after hatching (Gregg 1984). During cool, wet weather, chicks require constant brooding by females; prolonged periods of inclement weather may lead to substantial mortality of chicks (Dwyer et al. 1988). This reproductive strategy led Pettingill (1936), Mendall and Aldous (1943), and Sheldon (1967) to speculate that renesting by American Woodcock is common, although they could not document this behavior. Renesting would seem necessary to maintain adequate recruitment because American Woodcock clutches are small (3-4 eggs), nest success is 50-67% (Mendall and Aldous 1943, Gregg 1984), and chick survival is 59% (Dwyer et al. 1988). Renesting after loss of a clutch has been documented for other shorebirds, including the Eurasian Woodcock (Scolopax rusticola; Hirons and Owen 1982), plovers (Charadrius spp.; Warriner et al. 1986), Spotted Sandpipers (Actitis macularia; Lank et al. 1985, Oring and Lank 1986), Killdeer (Charadrius vociferus; Brunton 1988), and Rednecked Phalaropes (Phalaropus lobatus; Reynolds 1987). Some shorebird species are polyandrous (Schamel and Tracy 1977, Lank et al. 1985, Oring 1985, Reynolds 1987), and a few species are double-brooded (Brunton 1988). Only circumstantial evidence of late-nesting birds (Ammann 1967, Parris 1983) and prolonged brood seasons (Rabe 1979) suggest that woodcocks will renest. We present the first definitive records of renesting by American Woodcocks during a single nesting season. We conducted this study on the 6,850-ha Baring unit of Moosehorn National Wildlife Refuge (NWR) near Calais, Maine, on the New Brunswick border. Dwyer et al. (1988) described the study area in detail. Female woodcocks were captured in mist nets on courting areas. Females on nests and those with broods were located by a pointing dog and captured with hand nets (Ammann 1977). All nesting females and females with broods '5 days old were radio-marked. Females were aged by wing-plumage characteristics (Martin 1964) and classified as 1 year old (SY) or -2 years old (ASY). We weighed each bird at the time of capture and attached a 3.5-4 g transmitter to its back by livestock-tag cement and a single-loop wire harness (Derleth 1986). We located birds daily from vehicles or on foot with portable receivers and handheld antennas. Lost birds were located from light, fixed-wing aircraft with antennas attached to the struts (Gilmer et al. 1981). We flew transects 3.2 km apart across the study area and ? 16 km beyond its borders. Transmitter signals were detectable ?0.8 km from the ground and 20 days of age. Her reproductive tract contained

European Starlings (Sturnus vulgaris) have recently invaded Arizona and breed in some areas but not in similar areas nearby. In Arizona, European Starlings commonly nest in cavities in saguaro cacti (Carnegiea gigantea) but do not excavate these cavities. To examine whether European Starlings compete with native woodpeckers for nest cavities in saguaros, we studied Gila Woodpeckers (Melanerpes uropygialis) and Northern Flickers (Colaptes auratus) in areas with European Starlings and in similar, nearby areas with no European Starlings. We determined which factors explained the variation in the number of nests of each species present on fifteen 10-ha plots. We also compared the location and dimensions of nest cavities used by each species to determine whether European Starlings use Gila Woodpecker nest cavities, Northern Flicker nest cavities, or both. We found that European Starlings compete with Gila Woodpeckers but not with Northern Flickers. This competition decreases the number of Gila Woodpeckers that nest in areas where European Starlings nest. European Starlings used Gila Woodpecker nest cavities, and there was a negative relationship between the number of European Starling nests and the number of Gila woodpecker nests that explained 46.7% of the variation in the number of Gila Woodpecker nests on the plots. European Starlings did not use Northern Flicker nest cavities, and we found no relationship between the number of European Starling nests and the number of Northern Flicker nests. In addition, the number of Gila Woodpecker nests was positively related to the number of large saguaros and negatively related to the slope of the plot. The number of Northern Flicker nests was positively related to the volume of ironwood (Olneya tesota). The number of European Starling nests was negatively related to the distance to agriculture and large lawns. Received 29 June 1989, accepted 4 December 1989. EUROPEAN Starlings (Sturnus vulgaris) were introduced into North America in 1890 and rapidly spread throughout most of the United States (Kessel 1953). They were not observed in Arizona until ca. 1946 (Monson 1948). In Arizona, European Starlings commonly nest in cavities in saguaro cacti (Carnegiea gigantea), but they do not excavate these cavities (Kessel 1957). Gila Woodpeckers (Melanerpes uropygialis) and Northern Flickers (Colaptes auratus) excavate these cavities in saguaros for nest sites (Gilman 1915, Bent 1939), and the nesting season of the European Starling overlaps that of the Gila Woodpecker and the Northern Flicker (Gilman 1915, Bent 1939, Royall 1966). Brenowitz (1978) observed European Starlings usurp nest cavities from three pairs of Gila I Present address: Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 USA. Woodpeckers. One pair of Gila Woodpeckers lost three successive cavities to European Starlings. European Starlings have been observed usurping nest cavities from Northern Flickers in New Hampshire (Shelly 1935), Maryland (Howell 1943), and Massachusetts (Bent 1950). European Starlings have also usurped nest cavities from many other species including Purple Martins (Progne subis) in Michigan (Allen and Nice 1952), Red-bellied Woodpeckers (Melanerpes carolinus; Kilham 1958) and Wood Ducks (Aix sponsa; McGilvrey and Uhler 1971) in Maryland, Acorn Woodpeckers (Melanerpes formicivorus) in California (Troetschler 1976), Eurasian Nuthatches (Sitta europaea) in Sweden (Nilsson 1984), and Buffleheads (Bucephala albeola) in British Columbia (Peterson and Gauthier 1985). Van Balen et al. (1982) concluded that by competing for nest cavities European Starlings decreased the number of Great Tits (Parus major) nesting in their study area in the Netherlands. Our objective was to determine whether Eu367 The Auk 107: 367-375. April 1990 This content downloaded from 157.55.39.78 on Sun, 19 Jun 2016 05:49:35 UTC All use subject to http://about.jstor.org/terms 368 KERPEz AND SMITH [Auk, Vol. 107 ropean Starlings competed with Gila Woodpeckers and Northern Flickers for next cavities in saguaro cacti, and if so, to evaluate the effects of this competition. European Starlings presently breed in some areas of Arizona but not in similar areas nearby. Therefore, we were able to study Gila Woodpeckers and Northern Flickers in areas with no European Starlings and in similar, nearby areas with various densities of European Starlings. To assess the effect of competition, we studied the relationship between the number of European Starlings nesting in an area and the number of Gila Woodpeckers and Northern Flickers nesting in that area. We examined the relationships between habitat variables and the numbers of nesting Gila Woodpeckers, Northern Flickers, and European Starlings to separate the effects of habitat and competition. We also compared the location and dimensions of nest cavities used by each species to determine whether European Starlings use Gila Woodpecker nest cavities, Northern Flicker nest cavities, or both.

We investigated patterns and causes of variation in clutch sizes in a guild of five species of temperate-nesting dabbling ducks (Mallard [Anas platyrhynchos], Northern Pintail [“pintail,” A. acuta], Gadwall [A. strepera], Blue-winged Teal [“teal,” A. discors], and Northern Shoveler [“shoveler,” A. clypeata]) during 1993-1995 in the Prairie Pothole Region of midcontinental North America. Clutch sizes (mean ± SE) were largest for teal (10.80 ± 0.03), followed in descending order by those of shoveler (10.31 ± 0.05), Gadwall (9.92 ± 0.04), Mallard (8.91 ± 0.04), and pintail (7.66 ± 0.06). In Mallard, pintail, and shoveler, predicted clutch sizes at onset of nesting exhibited minimal variation. Clutch sizes of Gadwall and teal displayed statistically significant variation among years at onset of nesting; pintail clutch sizes showed significant variation late in the nesting season. Clutch sizes declined seasonally in all species. Declines in clutch sizes of teal and shoveler were approximately linear; ...

LITTLE is known of the ecology of the Common Raven (Corvus corax) population that inhabits the narrow belt of mountains from north Georgia to northern Pennsylvania. This disjunct group is a remnant of a previously larger, contiguous population (A.O.U. 1957). To our knowledge, only one account of the food habits of this isolated population has been published. Murray (1949) reported the animal remains found below two cliff nests in Rockbridge County, Virginia. Included were the bones of flying squirrels (Glaucomys volans), gray squirrels (Sciurus carolinensis), a Norway rat (Rattus norvegicus), a Mourning Dove (Zenaida macroura), a Blue Jay (Cyanocitta cristata), a Ruffed Grouse (Bonasa umbellus), a snake, and remains of grasshoppers. Reports from other regions indicate that Common Ravens rely heavily on carrion (Ratcliffe 1962, White and Cade 1971, Dorn 1972). Some students believe the raven has considerable potential as a predator (Craighead and Craighead 1956: 339; White and Cade 1971; Dorn 1972). That ravens frequent garbage dumps is well-known (Bent 1946: 227-262). Our objectives of the research were to determine the food habits of Common Ravens in Virginia during two critical periods of the yearwinter and the nesting season. Of particular interest were (1) the importance of prey as a food source, (2) possible economic implications of their food habits, and (3) the importance of garbage dumps as a food source. The study was made possible by the discovery of a nocturnal winter raven roost and the relocation of the apparent nonbreeding segment of the roost following the dispersal of the winter roost at the beginning of the nesting season. A concurrent study of nesting habitat made possible a search of 20 active nest sites for castings. The research was conducted in the Ridge and Valley Physiographic Province of Virginia, a region of parallel ridges that rise 1000 to 2000 feet above the intervening valleys. The ridges are covered by oak forests (Braun 1967) while the valleys are interspersed forest and pastures. The numerous cliffs and remote woodlands have provided a refuge for the species at a time when its numbers were being reduced throughout the eastern United States.

We studied egg destruction by conspecifics in colonial Cliff Swallows (Hirundo pyrrhonota) in southwestern Nebraska. Between 8.5% and 19.6% of all nests lost at least 1 egg to an intruding conspecific. Egg destruction occurred when nests were left momentarily unattended, often during colony alarm responses. Birds that destroyed eggs maintained nests of their own, and usually nested within 75 cm of their victims. Egg destruction was not related to attempts to usurp nests. Over a third of perpetrators of egg destruction lost eggs from their own nests to conspecifics. Egg destruction occurred more often in nests initiated early in the nesting season and in nests with large clutch sizes. Egg destruction usually occurred during a victim's egg-laying or early during incubation and declined in frequency as incubation proceeded. Breeding in a colony's peak period of nesting did not afford an advantage to potential victims by diluting their chances of being victimized. Cliff Swallows seldom destroyed all of the eggs in a neighbor's clutch, usually destroying only 1 egg at a time even though other eggs were present. There was little direct evidence that egg destruction was associated with parasitic egglaying by Cliff Swallows, but nests with egg destruction were over 3 times more likely than nests in general to have an egg physically transferred into them. The costs of egg destruction to victims were obvious, but the benefits to destroyers of eggs were not. Egg destruction is possibly a prelude to physical transfer of eggs, reducing host clutch sizes and ultimately within-brood competition among host and parasitic nestlings. Males may also benefit by destroying a female's eggs during laying, thereby causing her to continue laying and remain sexually receptive to forced extrapair copulations. Incidence of egg destruction by conspecifics increased with Cliff Swallow colony size and thus, for potential victims, represents a definite cost of coloniality. Received 22 January 1988, accepted 26 June 1988. A POTENTIAL cost of colonial breeding is an increased number and proximity of neighbors that may interfere with one's attempt to reproduce. A dramatic form of reproductive interference is the destruction of eggs and chicks by conspecifics within the colony (Wittenberger and Hunt 1985). Potential destruction of eggs or chicks represents an enormous cost of coloniality. This cost is incurred routinely by some colonially nesting birds, especially skuas, gannets, and large gulls (Wittenberger and Hunt 1985, references therein). Conspecific interference centers on prefledged chicks, perhaps often to prevent giving care to unrelated offspring. Chicks can be attacked, killed, and eaten. Cannibalism is an important component of this form of reproductive interference (Wittenberger and Hunt 1985). A steady supply of available chicks presumably represents a major benefit of nesting in a colony for a cannibalistic individual. Less attention has been paid to egg destruction and its effects in colonial birds. Lesser Blackbacked Gulls (Larus fuscus; Harris 1964, Brown 1967, Davis and Dunn 1976), Herring Gulls (L. argentatus; Paynter 1949, Harris 1964, Brown 1967), Arctic Terns (Sterna paradisaea; Pettingill 1939), Carrion Crows (Corvus corone; Yom-Tov 1974, 1975), and Marsh Wrens (Cistothorus palustris; Picman and Belles-Isles 1987) are reported to steal, puncture, or eat eggs from nests of neighboring conspecifics. Egg destruction in Cattle Egrets (Bubulcus ibis) occurs when nesting materials are stolen and during fights (Siegfried 1972). In communally nesting Ostriches (Struthio camelus), Groove-billed Anis (Crotophaga sulcirostris), and Acorn Woodpeckers (Melanerpes formicivorus), eggs in a clutch are removed and destroyed by later-laying females, a manifestation of reproductive competition among females (Vehrencamp 1977, Bertram 1979, Mumme et al. 1983). Egg destruction can have major effects on the fitness of both destroyer and victim (see Wittenberger and Hunt 1985). We must understand fully both egg destruction and chick-killing, because their costs and benefits must be measured if we are to construct a coherent general theory for the evolution of avian coloniality. 737 The Auk 105: 737-748. October 1988 This content downloaded from 157.55.39.103 on Mon, 25 Apr 2016 07:00:08 UTC All use subject to http://about.jstor.org/terms 738 BROWN AND BROWN [Auk, Vol. 105 We discovered that colonial Cliff Swallows (Hirundo pyrrhonota) in southwestern Nebraska often destroy the eggs of conspecifics. Egg destruction varied with colony size and may affect the evolution of coloniality. Although the costs to a victim are clear, the benefits to an egg destroyer are not. We report on egg destruction in Cliff Swallows and examine the potential costs and benefits to both victims and perpetrators. Further, we investigated whether egg destruction was associated with alternate reproductive tactics such as intraspecific brood parasitism (Brown 1984, Brown and Brown 1988). Because Cliff Swallow nestlings are highly altricial and are very immobile prior to fledging, chick-killing of the kind described in colonial seabirds does not occur in this species. We therefore restrict our focus exclusively to consideration of egg destruction.

Mortality among breeding adult California Gulls (Larus californicus) was low and spread throughout the breeding season in five years of a six-year study. In one year, nesting habitat decreased by 65%, mortality was 3-11 times higher and was concentrated during the period of intense territorial defense. Apparently, some displaced gulls that attempted to reclaim territories near their previous nest sites encountered resistance from territory holders. This resulted in death from trauma, especially among relatively small birds. In general there was a tendency for deaths among females to predominate in the first half of the breeding season and among males, in the latter half. Unlike the situation in British Herring Gulls (Larus argentatus), I found no indication of increasing adult mortality at the end of the nesting season. Received 18 January 1988, accepted 24 August 1988. THE number of adult birds that die of unspecified causes in nesting colonies during the breeding season, although typically considered to be very low, is rarely quantified (Kennedy 1973, Coulson and Wooller 1976, Wanless 1983, Spear et al. 1987). I documented the extent, timing, causes, and sex distribution of mortality among adult California Gulls (Larus californicus) at Mono Lake, California (1983-1988). I suggest that an anomalous pattern of relatively high mortality in 1984 was associated directly with a major reduction in nesting habitat in the study area, and was promoted by the gulls' strong tendencies toward philopatry and nest-site te

THE study of bird species diversity has thus far been concerned primarily with nesting bird communities (MacArthur and MacArthur 1961, Karr 1968, Recher 1969, Kricher 1973). Comparable studies on winter bird communities are less frequent (but see Emlen 1972, Austin and Smith 1972). This is unfortunate because winter presents a very distinct series of stresses to avian populations, differing from those of the nesting season. In winter, birds in north temperate latitudes are concerned only with individual survival. There is no singing, courtship display, or nesting activities. Acquisition of food is of prime importance to birds occupying a winter environment characterized by short daylight hours and an ambient temperature usually many degrees below body temperature (Gordon et al. 1968). Migration testifies to the rigors of the temperate winter environment. Recent studies of avian population biology (Lack 1966, 1968; Fretwell 1969, 1972) emphasized the possible importance of the winter season as a regulator of population size. The objective of this paper is to examine the patterns of winter bird species diversity over a 2-year period in two ecosystems of the New Jersey Piedmont. Considerable attention has been paid to possible relationships between weather factors and avian population and diversity changes. It is hoped that the elucidation of patterns in winter bird species diversity will contribute a greater understanding to the importance of the winter season relative to population regulation and will also contribute to an increased understanding of how ecosystems function.

& K. H. Voous. 1960. The breeding of the Cayenne Tern or Yellow-billed Tern in Cura,ao in 1958. Ardea 48: 51-65. BOND, J. 1956. Check-list of birds of the West Indies (plus Supplements 1-24, 1956-1982). Philadelphia, Academy of Natural Sciences. BUCKLEY, F. G., & P. A. BUCKLEY. 1972. The breeding ecology of Royal Terns Sterna (Thalasseus) maxima maxima. Ibis 114: 344-359. , & . In press. Social behavior of Royal Terns. In Handbook of the birds of Europe, the Middle East and North Africa: the birds of the western Palearctic, vol. 4 (S. Cramp et al., Eds.). Oxford, Oxford Univ. Press. BUCKLEY, P. A., & F. G. BUCKLEY. 1970. Notes on the distribution of some Puerto Rican Birds, and on the courtship behavior of White-tailed Tropicbirds. Condor 72: 483-486. DACIUK, J. 1976. Notas faunisticas y bioecologicas de peninsula Valdes y Patagonia. XVII. Colonias de nidificacion de Egretta alba egretta (Gmelin) y Sterna eurygnatha Saunders recientemente encontradas en las coastas de Chubut (Rep. Argentina). Physis 35: 341-347. ESCALANTE, R. 1970. Notes on the Cayenne Tern in Uruguay. Condor 72: 89-94. . 1973. The Cayenne Tern in Brazil. Condor 75: 470-472. . In press. The Royal Tern as a breeder and migrant on the Atlantic Coast of South America. In Neotropical ornithology (P. A. Buckley et al., Eds.). Ornithol. Monogr. JUNGE, G. C. A., & K. H. Voous. 1955. The distribution and relationship of Sterna eurygnatha Saunders. Ardea 43: 226-247. KEPLER, C. B., & A. K. KEPLER. 1977. The seabirds of Culebra and its adjacent islands, Puerto Rico. Living Bird 16: 21-50. NORTON, R. 1982. West Indies Region, nesting season 1982. Amer. Birds 36: 1019-1020. SICK, H., & A. P. A. LEAo. 1965. Breeding sites of Sterna eurygnatha and other seabirds off the Brazilian coast. Auk 82: 507-508. Voous, K. H. 1968. Geographical variation in the Cayenne Tern. Ardea 56: 184-187. 1983. Birds of the Netherlands Antilles, second ed. Zutphen, Netherlands, De Walburg Pers.

THIS study was designed to evaluate the habita.t relations and habitatniche usage of the warblers (Parulidae) in the Raleigh, North Carolina region during the spring migratory period. Although the general pattern of warbler migration has been studied extensively and the timing of first arrivals and peaks established for most species, no detailed studies have been made on habitat associations during migration. This paucity of information appears to be due prima,rily to the difficulty of measuring populations during migration and to the general belief that birds a-re much less selective of habitat during migration than in the nesting and winter season.s. Most habitat association studies have been made during the nesting season and in winter when populations are more stable. Many warblers have been shown to have clearly defined behavioral adaptations that limit them to particular habitats or parts of habitats on the nes.ting grounds (MacArthur, 1958). Further it has been demonstrated that the functional anatomy of the legs of some warblers makes. possible specific adaptations for particular methods of feeding (Osterhaus, 1962). As these adaptations do not change during migration, some degree of habitat selection should also operate at this time. Some lessening of the strength of selection can easily be understood, as the preferred habitats may be absent from portions of the migratory pathway. Also the internal pressures of migration may result in lessened consideration of all but the most urgent physiological needs. Most small passerine birds are nocturnal migrants and spend the daylight hours feeding. During these stopover periods each species would be expected to select those conditions most closely approximating its optimum, where it is able to feed most effectively. Habitat is genera.lly defined as the place where an organism lives. (Odum, 1959) and is usually described at the level of the major plant community, such as deciduous forest. It has long been realized that birds are associated with particular habitats, but only recently have detailed studies been undertaken to evaluate habitat selection among birds. Many life history studies were conducted in the early 19,00s, but these usually allude only briefly, if at all, to the bird's habitat. A major exception to this, concerning warblers, is Chapman's "The warblers of North America" (1907), which refers generally to the habitat of ea,ch species on the nesting grounds and in a few instances mentions the habitat frequented during migration. Stewart and Robbins (1958) also give a systematic but limited account of the habitat occurrences of warblers during migration. Recently habitat

THE social behavior of the Pintail, Anas acuta, seems to diverge most noticeably from that of other North American ducks of the genus Anas during the nesting phase of the reproductive cycle. This study examines the reproductive cycle of the Pintail with particular emphasis on the motivation and function of aerial activity which can be observed throughout the nesting season. Aerial activity during pair formation and nesting in ducks has been discussed by Hochbaum (1944), Sowls (1955), Dzubin (1955, 1957), Lebret (1961), Wiist (1960), Hori (1963), and McKinney (1965). Nonreproductive activity among young Pintails was observed to serve as a basis for comparison with reproductive behavior.

IN the study of nesting Chimney Swifts, Chaetura pelagica L., which occupy the air shafts of three adjacent buildings on the Kent State University campus at Kent, Ohio, observations were made on one bird and its mates which persistently nested in a hazardous situation. In spite of the fact that the nest was placed so near the top of the shaft that it was washed off by heavy rain before nesting was completed, the birds continued to build the nest in the same precarious position for four consecutive years. Each year the same accident was repeated. The life history of the male (No. 42-188516) and its mates just preceding and during those four years will be traced. The method of study and the life history of several other individuals have already been published (Dexter-Audubon Mag., 52:158-161, 1950; BirdBanding, 21:99-104, 1950; Ohio Journ. Sci., 51:42-46, 1951; Amer. Midl. Nat., 46 :227-229, 1951). Swift No. 42-188516, which will be referred to as No. 16, was banded on June 5, 1947, in air shaft B 1. At that time it was trapped with another bird which was banded No. 42-188515. Although these two roosted side by side each night for nearly three weeks, they failed to construct a nest. In the evening of June 30 only a single individual spent the night in B 1. Two nights later there were again two birds roosting there, but on different walls, and they proved to be No. 15 with another swift, No. 42-188524. After that date the swifts abandoned that shaft. No. 16 was not found again during the season. In September after the nesting season; No. 15 was retrapped on two different occasions with a small group of Chimney Swifts in shaft N9. No. 16 returned to B1 on May 9, 1948, at which time he was alone. After May 17 two birds were roosting there; four days later Nos. 15 and 16 were again trapped together from this shaft. However, they soon separated and were never found together again. No. 15 was found alone in shaft L3 on May 31. The next night it was in the adjoining shaft L2 with swift No. 42-188518, but once more dropped out of sight until after the end of the nesting season when it was for a second year found with a group of swifts in shaft N9. A foot injury to this bird (the band had slipped down over the toes, causing them to coalesce with a loss of the nails) may have interfered with normal nesting. The band was transferred to the opposite leg when the injury was discovered upon her return in 1948. This is the only case of such injury observed in banding more than 500 swifts. Possibly the

THIS paper on the food habits of the King Rail (Rallus elegans) is a continuation of a life history study of this species in the Arkansas rice fields (Meanley, 1953). Specimens and data on feeding behavior were obtained from 1950 to 1955. Most of the stomachs representing the nesting season were taken from dead rails found along local highways; winter specimens were furnished by Carl Kitler, local mink trapper who caught about one a day along his trap line. I am indebted to U. S. Fish and Wildlife Service co-workers E. R. Kalmbach, Alexander C. Martin, Robert T. Mitchell, and Francis M. Uhler for the identification of several food items found in gizzards; and to Dr. Martin, Johnson A. Neff, Charles C. Sperry, and Robert E. Stewart for reviewing the manuscript. Feeding Behavior.-During April, May, and early June it is not unusual to see 15 or 20 King Rails in the evening feeding along ditches bordering certain highways leading out of Stuttgart, Arkansas. After the middle of June, the rails move out of the roadside ditches and canals into adjacent rice fields where they are found until harvest. During the winter they are found about the network of rice field canals and natural drainage, spending much of their time along runways beneath matted vegetation. The most active feeding periods appeared to be in the early morning and the late afternoon or evening, usually till dusk. Rails were also found to feed sporadically throughout the day, tapering off or stopping for short rests during periods of intense heat. I once kept a pair of rails under constant observation for 2 hours while they fed in the vicinity of their nest during the middle of the day. The feeding bird passed back and forth near the nest and often came within a few inches of its incubating mate. On other occasions individuals seen feeding steadily for a half hour or more along a ditch during the heat of midday in June stopped under a tussock of grass and remained motionless for from 5 to 20 minutes before resuming activity. Rails do most of their feeding in places concealed by plant cover or in relatively open areas where they blend well with their surroundings. Occasionally, however, the birds are very conspicuous, as when feeding on mud flats or in recently flooded fields where rice sprouts are 3 or 4 inches in height. W. Leon Dawson (1903: 443) observed similar rail-feeding activity in open areas in Ohio: "In a region where

THE concepts of species-specific characteristics and social releasers as developed by ethologists (see Tinbergen, 1951; 1959: 318-330) have intrigued animal behaviorists as much as any concept in the science of ethology. Utilizing these concepts, I have been engaged since 1959 in studies of the behavior of parakeets of the genus Aratinga, primarily A. c. canicularis, the Orange-fronted Parakeet, and also recently other forms. The acquisition, in 1960, of captive birds of A. c. eburnirostrum and, in 1962, of 12 Aratinga astec, the Aztec Parakeet, made possible experiments and observations on the function of morphological and behavioral characteristics which are involved in sociality. The results of these studies have bearing upon our understanding of psittacid evolution. Elsewhere (1963) I have described the epigamic and reproductive biology and (1965) the flock social behavior of A. canicularis. This parakeet is highly social in the wild except during the nesting season, when pairs disperse to nest. Flocks of 5 to 50 birds are otherwise common throughout the species' range, and groups of up to 12 or 15 birds typically wander about between scattered feeding areas and resting sites. The range of the species extends from northern Sinaloa, Mexico, south into the Central American lowlands and the foothills of the Pacific coast in tropical deciduous forest. Three well-marked populations occupy this range. These are designated subspecifically as clarae in the north, eburnirostrum from Michoacan to Oaxaca, and canicularis in the south (Friedmann, et al., 1950: 126). The last two races mentioned are to be considered here. They are easily separable, the former having less orange on the forehead and a blackish splotch on the lower mandible, while the latter has a large patch of orange on the forehead and only the faintest wash of gray on the lower mandible (see extreme left and right subjects in "Step 7," Figure 1). Aratinga astec may be considered the ecological counterpart of A. canicularis in similar (but more mesic) habitat on the Atlantic slopes of Mexico and Central America. A. astec averages slightly smaller and is generally similar to A. canicularis in plumage, but lacks markings of orange, blue, and black on the head. In Aratinga astec, only a tuft of orange feathering is found above the cere. In captivity, the two species as observed by me were much alike in habits, including feeding, degree of sociality, agonism, epigamy, and voice. Although little published information is available concerning Aratinga astec, its biology in the wild state probably is closely similar to that of A. canicularis. All evidence in

OBSERVATIONS on the nesting and laying of the Woodpeckers (Picidae) and the Vultures (Cathartidoe) have shown several very interesting phenomena. The following will be an effort to bring out the rather peculiar and often unexpected actions on the part of these birds without any attempt to go into detail or record the many familiar nesting habits that are well known to all ornithologists. The notes are taken entirely from my data that were made while collecting and observing in the field in the east central and southwest portions of Mississippi. Ceophlceus pileatus. PILEATED WOODPECKER.-This bird has become rare in many parts of Mississippi but is still rather common in certain portions. During three seasons seventeen nests were watched in Adams County. In the vicinity where observations were made every small woods had its pair of these large woodpeckers. The individuals of this species seemed to occupy very small feeding areas. Of the seven nests that were found in 1902 five pairs of the birds were located in their respective woods during the previous December and January. Whenever a pair was once seen feeding in a wood during the winter the same pair could always be found very close to that place. At the beginning of the nesting season they would invariably make their burrow in some dead but sound tree near the edge of the brake. From continued observation it appeared certain that whenever a pair were found in a small wood during the winter they were sure to nest there the following spring. The burrow is very large and requires in most cases about one month for construction, being commenced in this locality about the latter part of February. But it was found very difficult to note the exact length of tiine consumed in burrowing, as the birds try so many parts of the same tree before striking one to suit their taste. The nest tree and other dead trees close at hand were often scarred from top to bottom. In two cases they began a nest, then seemed to start one in another place, and then returned

cutting, a Solitaire flew off her nest and passed in front of the car. Her nest was in a small crevice in the rock cutting, five feet above the road, and would have been on the level of a man's eye• walking along the ground. The nest was built of dry grass, twigs, fine roots and moss: lined with fine grass and contained four partly incubated eggs. The young are slim handsome birds conspicuously spotted with silvery buff on the lower parts, head and back. The alarm not;e is similar to the "chuck chuck" o• the Hermit Thrush. In a recent number of the Condor, • Mr. Forrest S. Hanford states, that during thirteen years, he has heard the •%litaire sing only five times. In this district, they sing quite freely, during the nesting season; generally perched on the very top of a Douglas fir or Murray pine. I have frequently heard them singing in the winter. In the winter months their food is largely the acrid berries of the dwarf juniper (•uniperus occidentalis).

THE distribution of most raptorial birds during the nesting season indicates that they set up relatively large territories from the limits of which all other individuals of their kind are vigorously excluded. In few species is this habit more conspicuous than in the Great Horned Owls, Bubo virginianus. Field studies at Lawrence, Kansas, during 1932 and the spring of 1933, and at Ithaca, New York, from the fall of 1933 to the spring of 1936 strongly suggest that this intolerance to overcrowding is an important factor in determining the density of population. All the evidence available indicates that the Great Horned Owl holds a definite territory throughout the nesting season and that in many cases the male takes up his station in this area in the late fall or winter before the period of courtship and mating begins. Certain individuals appear to roost regularly in the same place throughout the year, but since they are not always found in their usual 'hideouts' it is questionable if the territorial instinct is operative during a period of several months following the nesting season. In addition to patrolling the nest territory against all invaders the owls apparently restrict their hunting to this same area. Occasionally a bird may go on a longer foraging trip, but at nests where unhoused poultry is not available within a half mile or so such raids are rarely or never undertaken. A number of field observers have noted the fact that Horned Owls have definite limits to their range. Ridgway (1874) states that these owls rarely go more than a mile from their nests and then only for food. Bendire (1892) quotes Denis Gale as follows: " Each pair of these birds has their particular range and no amount of harassing or robbing them of their eggs two or three times a year will induce them to leave a locality once chosen. The food supply, of course, is the chief consideration influencing their choice. In some cases half a mile of creek bottom defines the limit of their preserve or hunting ground, and occasionally it is larger . . . A choice of location once made is never abandoned unless civilization blots out the cover or kills the birds." Miller (1930) made observations indicating that two Pacific Horned Owls had definite territories which they held in late June. Each bird appeared to patrol an irregular-shaped area with the longest diameter approximately half a mile. An attempt was made to bring the two birds together by 'hooting' from a point between their territories but the effort met with no success. Apparently both birds respected the rights of their neighbors and neither would approach closer than seventy-five yards from this boundary.

FOR probing into some aspects of bird navigation, such as the parts played by learning and by individual variation, it becomes necessary to use the same birds repeatedly on homing flights. Pigeons have been used in this way (e.g., Matthews, 1952b; 1963) but, despite intense artificial selection over the last century, they are inferior in navigational ability to wild, long-distance migrants. Wild birds, however, are liable to desert their nests if subject to repeated disturbance during the nesting season; finding the same bird in succeeding years is often difficult; and the smaller species are in any case short-lived. Leaving aside birds repeatedly retrapped in winter after being displaced short distances, the literature has little to offer on the study of individual navigation. Watson and Lashley (1915) record repeated sorties of 3 Noddy Terns (Anous stolidus) and 1 Sooty Tern (Sterna fuscata); Riippell (1935) of 20 Starlings (Sturnus vulgaris); Wojtusiak and Ferens (1938) of 15 Swallows (Hirundo rustica); Lack and Lockley (1938) of 2 Manx Shearwaters (Puffinus puffinus Procellaria puffinus of European literature); Griffin (1943) of 7 Herring Gulls (Larus argentatus); Matthews (1952a) of 4 Lesser Black-backed Gulls (L. fuscus) and 1 Herring Gull; Spaepen and Dachy (1953) of 7 Swifts (Apus apus); and Sargent (1962) of 19 Bank Swallows (Riparia riparia). Nothing very conclusive derived from the results of these studies. In most cases the birds were released at the same place both times. In 22 cases the second return was then faster, but in 22 cases it was slower or the bird failed to home. The Bank Swallows, which were released at different points, "generally showed better homing success than those released for the first time" (Sargent, 1962: 237). The Manx Shearwater (Puffinus puffinus puffinus), besides being an accomplished navigator, is a long-lived bird which returns to the same, easily accessible nesting burrow year after year. Homing experiments were therefore carried out with this species from a colony on Skokholm Island (510 42' N, 050 17' W) in four successive breeding seasons, May to July. The general and experimental results have already been reported (Matthews, 1953b; 1955a, b); this paper presents and interprets the data obtained from repeated releases of individual birds.

Nuthatches of the genus Sitta constitute one of the passerine groups in which prealternate (prenuptial) molt is generally believed not to occur. Dwight (1900: 298) discussed this genus with the family Paridae and stated: "All the members of this family have only the annual moult. They are peculiar in assuming a juvenal plumage closely resembling the pale nuptial plumage which results from extreme fading of the winter dress. " Witherby (in Witherby et al. 1938: 244) remarked that in S. europaea the summer plumage is attained by abrasion rather than by molt. Following Dwight's analysis, Bent (1948) recorded that the prenuptial molt did not occur in S. carolinensis or S. canadensis. Although Norris (1958: 246) found several females of S. pygmaea that were replacing feathers in the nuchal region in March and April, he regarded this as a regrowth of feathers lost in social interactions rather than as prealternate molt; the replacement of contour feathers "over nearly every part of the body" in early April by one female of that species was considered to be "an aberrant instance of prenuptial molt." Norris (op. cit.) stated categorically that "There is no prenuptial molt in Sitta pusilla." For most species in the genus, however, I have been unable to find any statement, even a negative one, concerning the occurrence of this molt. On the other hand, there is a partial prealternate molt in the seasonally dimorphic Tichodroma muraria, usually considered a member of the family Sittidae but in a different subfamily. While studying Red-breasted Nuthatches, S. canadensis, for other reasons (Banks 1970), I noticed a spring-taken female that was replacing several ventral feathers. Examination of additional specimens revealed that a partial prealternate molt is of common occurrence in that species. To determine the occurrence, extent, and timing of the molt in the genus Sitta, I subsequently examined most of the seasonally appropriate specimens of nuthatches in the U.S. National Museum of Natural History and the American Museum of Natural History. Through the courtesy of George Watson, I was able to examine specimens from the Yale Peabody Museum that he had collected in the Mediterranean region. Additional specimens were studied at the Musee Royal d'Historie Naturelle in Brussels. A combination of several problems necessarily makes a survey such as this less complete than is desirable (Lanyon 1975). Relatively few persons collect extensively in the months just prior to the onset of breeding, so that population samples are small in the months when prealternate molt might be expected. For some species the material available is too scanty to permit any conclusions to be drawn. Pin feathers are often lost as a specimen is prepared, and if only a few feathers are involved in a partial molt, as seems often to be true in nuthatches, this loss may obscure the occurrence of the molt. Lack of precise information on the time of breeding and of the annual prebasic molt in a species renders it impossible to look specifically for prealternate molt; this situation occurs particularly where there is reason to believe that the onset of breeding is determined by factors other than those that operate in the temperate Palearctic regions. In general, I examined birds taken in the months of February through May for evidence of prealternate molt. This selection of dates proved inadequate for some nuthatch populations of southern Asia and the Philippine Islands, where the nesting season differs from that of nuthatches in temperate areas. Where prealternate molt occurs in a very small proportion of a population, and where it may involve only a few feathers in the molting individuals, it is difficult to distinguish between a true molt and the replacement of feathers fortuitously lost. Some errors of judgement may have resulted from this difficulty, particularly in species represented by small samples. For the reasons mentioned, and various combinations thereof, the fact that I did not find evidence of prealternate molt in certain species or populations of nuthatches should not be taken as a definitive statement that no such molt occurs. It is hoped that the preliminary results reported here will stimulate study by those who have access to appropriate material. The arrangement of the species in the accounts that follow is not meant to be phylogenetic or to imply any concept of relationship. For convenience and because the information is more complete, North American species are listed first. Not all forms in the genus were examined. Species listed by Greenway (1967) but not in this paper are considered to be races of species discussed. Sitta canadensis. -Prealternate molt in the Red-breasted Nuthatch varies from slight (perhaps none in some individuals) to extensive. Most feather replacement occurs on the ventral surface, with the malar

Le gite communal d'A.o. observe est situe dans le sud-est de l'Idaho. Liste commentee des proies

THE breeding range of the typical form of the Evening Grosbeak (Hesperiphona vespertina vespertina) is at present very imperfectly known. There are records of birds seen in summer in Alberta, Manitoba, Minnesota, and extreme western Ontario and of young not yet fully fledged in both Alberta and Manitoba; but the only fully authentic nest found is one discovered by Mr. S. S. Stansell about thirty miles northwest of Edmonton, Alberta. The writer's discovery of five nests of this species in northern Michigan is therefore of much interest. Evening Grosbeaks are found to be fairly common in favored sections of Michigan in fall, winter, and early spring, but disappear with the approach of the nesting season. Flocks of these forest dwellers were observed in November, 1920, in the Taquamenaw River district, Northern Peninsula of Michigan, to which locality they were evidently attracted by the heavy beech mast. The birds were generally observed earnestly feeding in the top branches of the hardwood trees. Observation and inquiry in the summer of 1921 gave no hope of finding the birds nesting, and it was, therefore, an agreeable surprise when, in July, 1922, a nesting colony was located on Whitefish Point, Lake Superior, about 20 miles from the Canadian shore. It is fitting that a place so far-famed as Whitefish Point should be selected as a nesting place by these elusive wanderers, but from available information it seems that they had never before, during the recollection of present inhabitants, so favored it. The site chosen is an impressive and interesting one and truly in harmony with the beauty and dignity of the birds. The beauty of the northern woods, especially where the white pine grew, has been greatly impaired by lumbering, not only as a result of the removal of the trees, but because, where extensive lumbering was done, forest fires invariably followed the logging. It is not improbable that the cutting of the pines influenced the birds that might have