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Eastern Purple Martins (Progne subis subis) have an unusually close relationship with humans, as they nest exclusively in man-made nest boxes. Current conservation policy directly promotes further interaction with this species by advocating regular replacement of nest materials during the nestling phase to reduce ectoparasite load and increase nestling fitness. We conducted the first test of the efficacy of this recommendation and found that it was partially effective in reducing parasite abundance, but had no effect on nestling fledging success, body mass, leukocyte count, or triglyceride or uric acid concentration. We found a small but significant increase in nestling hematocrit associated with nest material replacement, implying that parasites may induce nestling anemia. Contrary to our expectations, we also found elevated heterophil/lymphocyte ratios in nestlings with replacements, possibly indicating elevated physiological stress associated with nest replacements. Based on our results, we do not recommend nest material replacements to combat routine parasite infestations.LAY SUMMARYPurple Martins are believed to have a high abundance of blood-feeding parasites (fleas, mites, and blowfly larvae) in their nests.A current conservation policy recommends that nest box managers regularly remove and replace nest materials during the nestling phase to reduce parasite abundance. We tested the efficacy of this policy.Nest replacements reduced flea and blowfly larvae abundance, but mite abundance rebounded quickly.There was no difference in fledging rate, body mass, white blood cell count, or triglyceride or uric acid levels for nestlings with or without nest replacements.Nestlings with nest replacements were less anemic and had a higher ratio of heterophils to lymphocytes.

Road edges in the temperate zone often negatively affect reproductive success, post-fledging survival, and dispersal of forest birds through processes associated with edge habitats. This pattern is less clear in the tropics due to a lack of studies using natural nests and radio-tagged fledglings as well as an almost complete absence of information on nest and fledgling predators. We investigated the influence of road edge on nest success, post-fledging survival, and dispersal of White-rumped Shama (Copsychus malabaricus) in a dry evergreen forest in northeastern Thailand. One hundred nest boxes were placed in forest interior (≥1,000 m from edge of a 5-lane highway) and 100 near forest edge (≤200 m) to assess nesting success. We radio-tracked 50 fledglings from these boxes, 25 each for edge and interior, for 7 weeks after fledging. Nest success and post-fledging survival were 11.6% and 23.6% higher at the edge versus the interior. Predation had the strongest influence on survival, accounting for 100% of nest and 94% of fledgling mortality. Fledglings used locations with denser understory vegetation cover relative to the available habitat, probably to reduce predation risk. Green cat snake (Boiga cyanea) and northern pig-tailed macaque (Macaca leonina), which likely prefer forest interiors over edges, were the primary predators of nests and fledglings in this landscape. There were no significant differences in timing of dispersal and dispersal distance or dispersal direction in relation to proximity to edge. Our results suggest that the impacts of edge effects on the reproductive success of birds appear to be strongly dependent on the habitat preferences of locally dominant predators. Further research will be needed to identify key predators and broadly assess their foraging behaviors in individual landscapes.

Rusty Blackbird (Euphagus carolinus) populations have plummeted since the mid-20th century. Recent research in New England, USA, suggests that an ecological trap, created through timber harvesting on the breeding grounds, may be responsible. Red squirrels (Tamiasciurus hudsonicus) were hypothesized to be the primary nest predator, but definitive identification was lacking. The potential for mast cone crops to affect Rusty Blackbird nest predation via trophic interactions also remains unexamined. Our objectives were to identify the mechanisms by which an ecological trap may be operating in New England through a multiscale analysis of Rusty Blackbird habitat selection and nest survival, as well as predator identification and quantification. We located 72 Rusty Blackbird nests in Maine and New Hampshire in 2011 and 2012, and modeled habitat selection and nest survival as a function of habitat characteristics at the nest patch (5 m) and home range (500 m) scale. We placed camera traps at 29 nests to ...

In species that defend all-purpose breeding territories, territory size is usually inversely related to food abundance, but it is unclear whether this relationship results from reduced need to defend a large territory if food is abundant or from greater competitive pressure from conspecifics. Although studies of both breeding and winter territories suggest that competitive pressure is the proximate determinant of territory size, with food abundance acting indirectly by increasing the density of competitors, results are often equivocal because competitor density and food abundance tend to be positively correlated. In the Tree Swallow (Tachycineta bicolor), an aerial insectivore that defends only nest sites, defense of a food supply is not a determinant of territory size. I describe two series of experiments involving manipulation of nest-box spacing and measurements of insect abundance at four sites at and near Long Point, Ontario, Canada. Rates of occupancy of nest boxes spaced 24 m apart (beyon...

Young, immature-plumaged males of species in which plumage maturation is delayed are often unable to obtain mates or pair later in the season to lower-quality females. Their clutches are smaller and the quality of their eggs is lower, leading to fewer nestlings, whose quality and fledging success are reduced. The Saffron Finch (Sicalis flaveola) is an understudied and declining secondary-cavity nester with delayed plumage maturation; yearling males look like females. The aims of this study, of birds nesting in boxes, were to compare the morphology of immature- and mature-plumaged males of the Saffron Finch and their respective females and to compare the breeding success of females mated to each category of male. We expected that females mated to immature-plumaged males would follow the pattern described for other species, having lower reproductive investment and success. Immature- and mature-plumaged males were similar in morphology, but females paired to mature-plumaged males were bigger in bil...

Alexander Skutch suggested that the threat of nest predation on tropical birds favors reduced activity near their nests. This hypothesis assumes that nest predation occurs during the day when adult birds are active, but few studies of tropical species have reported distributions of nest losses during the day-night cycle. We used thermistors placed in nests to record the time of nest predation events for species of understory rainforest birds during the incubation period. In our study, 14 of 21 nest-predation events (67%) occurred between 11:00 and 18:00 (EST), and none took place at night, between 19:00 and 06:00. Clearly, nest predation during incubation was primarily diurnal. Although a major premise of Skutch's hypothesis is supported, further research is needed to determine whether diurnal predators are attracted to nests by the movements of parent birds, begging of offspring, or other cues.

We studied the foraging ecology of a population of Tree Swallows (Tachycineta bicolor) breeding in New York State over a period of 5 years. While feeding nestlings, adult Tree Swallows tended to spend most of their time within sight of their nest box and less than 12 m above the ground. Major insect taxa captured include Diptera, Hemiptera, and Odonata, ranging in length from mainly 0-10 mm, with some individuals up to 60 mm. The sex of the parent delivering the food had no significant effect on diet composition. Selection for or against food categories was determined by comparing the proportion of insects of different types in the diet of Tree Swallows to the proportions available in the air column. Tree Swallows showed consistent selection for insects larger than 3 mm and against smaller insects, especially Diptera in the suborder Nematocera. Only minor differences in diet were observed among years, and the effects of the abundance of food available were generally small. The patterns of selectivity found in this population were consistent with those found in previous studies on this species carried out in other locations, and these patterns are likely the result of differences in the profitability or visibility of prey types.

Artificial nests frequently are used to assess levels and patterns of nest predation, but how well these nests measure rates of predation or trends in predation rates at real nests is unclear. We compared predation rates between 58 active Wood Thrush (Hylocichla mustelina) nests paired with 58 artificial nests designed to resemble Wood Thrush nests. Paired nests were available to the same predator community both spatially and temporally. Rates of nest predation were significantly lower for active Wood Thrush nests (33%) than for artificial nests (64%). Rates of parasitism by Brown-headed Cowbirds (Molothrus ater) also differed between the two groups. Twenty-six percent of active nests and none of the artificial nests were parasitized by cowbirds. During 1993 and 1994, we conducted three artificial nest trials on six study sites per year. Rates of predation were highest in small woodlots and declined with increasing forest patch size consistent with the trend reported for active nests on the same sites. Within sites, rates of predation varied among trials with the amount of variation highest on sites with high predation rates. Our results suggest that although artificial nests should not be used to measure actual rates of nest predation or parasitism, they may be valuable for detecting trends in rates of predation. However, because there are many potential biases associated with the use of artificial nests that may make interpretation of trend data difficult, we recommend using artificial nests primarily in pilot studies or in conjunction with active nests.

We evaluated the consumption of Japanese Quail (Coturnix coturnix) eggs by captive reptiles, birds, and mammals in order to examine potential bias of nest predation experiments, and to determine whether predator identification through egg remains is reliable by the commonly used methods. Because none of the 86 individuals of 22 species of snakes consumed quail eggs in captivity, nest predation may be under-represented in artificial nest experiments. All three groups of predators left all types of egg remains, suggesting that researchers should refrain from classifying nest predators only hy egg remains. The presence of scratches on quail eggs could be considered as a potential tool for reducing small-mouthed mammal bias on predation estimates in small-sized eggs in nest predation experiments.

The object of this review is to relate nest-building behavior to the origin and early evolution of passerine birds (Order Passeriformes). I present evidence for the hypothesis that the combination of small body size and the ability to place a constructed nest where the bird chooses, helped make possible a vast amount of adaptive radiation. A great diversity of potential habitats especially accessible to small birds was created in the late Tertiary by global climatic changes and by the continuing great evolutionary expansion of flowering plants and insects. Cavity or hole nests (in ground or tree), open-cup nests (outside of holes), and domed nests (with a constructed roof) were all present very early in evolution of the Passeriformes, as indicated by the presence of all three of these basic nest types among the most primitive families of living passerine birds. Secondary specializations of these basic nest types are illustrated in the largest and most successful families of suboscine birds. Nest site and nest form and structure often help characterize the genus, as is exemplified in the suboscines by the ovenbirds (Furnariidae), a large family that builds among the most diverse nests of any family of birds. The domed nest is much more common among passerines than in non-passerines, and it is especially frequent among the very smallest passerine birds the world over. Each basic type of nest built by passerines has advantages and disadvantages in specific ecological situations, and nest type depends on a balance of multiple factors that involve the nest site, the physical environment, the community, and the size and behavior of the birds.

Artificial ground nests were placed in medium-age or older forests adjoining (a) stands of regenerating forest (vegetation < 2 m high) where 'hard' edges were created, and (b) stands of young forest (vegetation 2-8 m high) where 'soft' edges were created. Nests were placed at three distances from the forest edge (0 m, 50 m, and 100 m). Two Northern Bobwhite Quail (Colinus virginianus) eggs were placed in each nest and monitored after 7 and 14 days of exposure between late May and mid-July, 1994. Overall nest predation was 72% after 7 days and 85% after 14 days of exposure. Predation near soft edges was significantly higher than near hard edges after both 7 and 14 days of exposure. Predation near the edges was significantly higher than away from the edges after both 7 and 14 days of exposure. Two motion-sensitive cameras were used to record the identity of predator species. Cameras documented 28 predation events during 1,728 hours of operation, caused by eight species of mammals. The predators included, in order of decreasing predation: fisher (Martes pennanti), Eastern chipmunk (Tamias striatus), red-backed vole (Clethrionomys gapperi), red squirrel (Tamiasciurus hudsonicus), deer mouse (Peromyscus maniculatus), black bear (Ursus americanus), gray squirrel (Sciurus carolinensis), and striped skunk (Mephitis mephitis). The relationship between edges, predator assemblages, and nest success is complex; more studies at the landscape level are required to better understand the effects of these factors on avian population dynamics.

One possible link between livestock grazing and bird population declines is variation in nest predation rates. To explore this possibility we documented vegetational differences in a montane riparian community subdivided by a fence, one side of which traditionally has been summer-grazed, and the other side rested from grazing for 30 years. We found that ground vegetation was more abundant, willows (Salix spp.) less abundant, and vertical vegetational diversity was lower on the grazed relative to the rested side. Predation rates on real nests were higher on the grazed side compared to the rested side. Artificial nests were placed (I) in mixed conifer vegetation to mimic the most common nest types currently present in the riparian zone, (2) in streamside willows that differed in abundance across the fence, and (3) in old-willow remnants distant from the stream, which were equally abundant on both sides of the fence. All artificial above-ground nests, and ground nests in the old-willow experiment, suffered greater predation rates on the grazed compared to the rested side. Thus, livestock grazing may not only affect availability of nesting substrates for riparian birds by reducing streamside vegetation, but could influence bird populations by facilitating nest predation, possibly by increasing detectability of nests or through changes in predator assemblage.

Males of several species of wrens (Troglodytidae) participate to varying degrees in nest building, some even building multiple nests (Kendeigh 1941, Verner 1965, Collias and Collias 1984, Kennedy and White 1992). The Northern House Wren (Troglodytes aedon) is a monomorphic, insectivorous, secondary cavity nesting species which is seasonally monogamous although polygyny does occur (Kendeigh 1941, Drilling and Thompson 1988, Johnson and Kermott 1991). Male House Wrens build multiple nests within their territories by placing sticks into several cavities (Kendeigh 1941, McCabe 1965, Finch 1989), while one cavity is the focus of the male's attention and receives the most sticks (Kendeigh 1941, Belles-Isles and Picman 1986). Soon after a female arrives on the male's territory she constructs a soft nest of rootlets, grass, and feathers on top of the stick foundation into which she deposits her eggs (Kendeigh 1941, Kennedy and White 1992). Although females insert some sticks into cavities (Kendeigh 1941, McCabe 1965), it is the male that expends the most effort filling nesting cavities with sticks (Kendeigh 1941, Kennedy and White 1992). Two hypotheses advanced (Kendeigh 1941) to explain the function of this behavior were territorial claim and female choice. Since competition for suitable nesting sites may be high for cavity-nesting species (Yahner 1983/1984, Brawn and Balda 1988, Gustafsson 1988), by placing sticks into cavities first, early arriving males may outcompete later arrivals for a favorable nest site. In many monomorphic species, males may be subject to stronger sexual selection which may manifest itself in behavioral rather than morphological consequences (Andersson 1994). Females may therefore select males based on the extent to which the stick foundation is completed (Kendeigh 1941), and may evaluate a male's commitment to her and the nest site similar to the Black Wheatear, Oenanthe leucura (Moreno et al. 1994), perhaps reducing her chances of being a secondary female if mated with a polygynous male. The extent to which the sticks serve a specific function with regard to the nest structure itself has not been tested. By preventing males from filling treatment nest boxes with sticks, I tested two hypotheses. First, if filling a nest box with sticks by males is necessary for courtship and mating, then stick removal from boxes should preclude pair-bond formation. Second, if having a stick foundation enhances fledgling success in some way, than pairs with sticks removed should be less successful in rearing and fledging young.

boxes: facts and artifacts in nest box studies of birds? Oikos 56:421-423. MORENO. J., M. SOLER, A. P. MOLLER, AND M. LINDEN. 1994. The function of stone carrying in the Black Wheatear (Oenanthe leucura). Anim. Behav. 47: 1297-1309. PARREN, S. G. 1991. Evaluation of nest-box sites selected by Eastern Bluebirds, Tree Swallows and House Wrens. Widl. Soc. Bull. 19:270-277. VERNER, J. 1965. Breeding biology of the Long-billed Marsh Wren. Condor 67:6-29. WINKLER, D. W. 1993. Use and importance of feathers as nest lining in Tree Swallows (Tachycineta bicolor). Auk 110:29-36. YAHNER, R. H. 1983/1984. Avian use of nest boxes in Minnesota farmstead shelterbelts. J. Minn. Acad. Sci. 49:18-20.

Researchers studying hole-nesting birds breeding in nestboxes typically remove old nests from boxes. In natural cavities, old nest material accumulates with successive use. Here, we report on a two-year experiment concerned with the effects of the accumulation ofused nest material in nestboxes on the reproductive success of Tree Swallows (Tachycineta bicolor). Tree Swallows nested in clean boxes, boxes with old, unmanipulated material, and in boxes with old nests that had been microwaved to kill parasites inside. Bird fleas (Ceratophyllus idius) were more numerous in boxes with old nest material compared to clean boxes in both years. Reproductive output and nestling size were significantly reduced in the second year of the study, possibly because of higher numbers of bird fleas in two box-types that year. However, all instances of entire brood loss that year occurred during two periods of extreme weather, so we cannot distinguish between the possible effects of parasites and climate. In one year, the swallows nested later in boxes with old material. Otherwise, nesting phenology, reproductive output, and nestling size were not different between pairs using boxes with and without old material in either year. In both years, there was a significant, positive correlation between clutch size and cavity size. Contrary to some recent studies, there were no significant associations between the numbers of fowl mites (Ornithonyssus sylviarum), bird fleas, or blowflies (Protocalliphora sialia) per nestling, and any measures of reproductive output or nestling size in either year. We discuss our results in light of a recent critique of studies of birds breeding in nestboxes.

We studied the thermal environment of Wood Duck (Aix sponsa) nests in southeastern British Columbia. Mean daily nest temperatures (T N ) were correlated with maximum daily air temperatures. T N increased as the egg-laying period advanced among both successful and unsuccessful nests, although T N was lower among unsuccessful nests. Hens began spending nights on nests when there were as few as four eggs in clutches. T N and the precision of nest thermoregulation increased among successful nests as the incubation period advanced, although there was a great deal of variation between days and nests. Length of the incubation period was not correlated with clutch size, nor with mean overall nest temperature during incubation, but was correlated with the variance of T N 's during incubation.

0.4 days between the thirdand fourth-hatched chicks. If these limited data are representative (no other detailed information is available), all chicks are well separated in the pattern of size differences initially produced within broods by hatching asynchrony. Firstlaid eggs averaged 2.6% less than second-laid eggs in volume, but it seems safe to infer that this difference must be of little importance in reducing the initial bodymass difference between firstand second-hatched chicks.

Several recent studies have documented repeated incidents of polygyny in populations of secondary-cavity nesting birds provided with an abundance of nest boxes (Dhondt 1987, Marks et al. 1989, Korpimiki 1989, Pinxten et al. 1989, Alatalo and Lundberg 1990, Petit 1991, and references in each). During a study of House Wrens (Troglodytes aedon) in Wyoming, we found that over half of males with at least two nest boxes on their territories became polygynous. Price (1986) and Quinn (1989) have also recorded high rates of polygyny among box-nesting House Wrens in Illinois and Alberta, respectively. In the Wyoming population, polygyny appeared to be costly to second-mated females because they received less parental assistance from mates and fledged fewer young than monogamous or primary females (in prep.). Reduced reproductive success for second-mated females has been documented in other boxnesting species including Pied Flycatchers (Ficedula hypoleuca; Alatalo et al. 1981, Stenmark et al. 1988), Blue Tits (Parus caeruleus; Dhondt 1987), Boreal (Tengmalm's) Owls (Aegoliusfunereus; Solheim 1983, Carlsson et al. 1987, Korpimiki 1991), European Starlings (Sturnus vulgaris; Pinxten and Eens 1990), Prothonotary Warblers (Protonotaria citrea; Petit 1991), and House Sparrows (Passer domesticus; Veiga 1990). To explain the occurrence of polygyny in these species, most researchers have invoked one of several formal models that outline conditions under which polygyny, although costly to fitness, can still be an adaptive choice made by females (Searcy and Yasukawa 1989). However, these models assume that polygyny evolved in situations where females were routinely faced with a choice of paired and unpaired mates. Alatalo and Lundberg (1984) cautioned that if in the "natural situation" the abundance and dispersion of suitable cavities is such that males rarely control more than one nest site, there may be little selection on females to identify and consider the pairing status of a potential mate. Thus, the seemingly maladaptive choice of polygyny made by females in box-nesting populations could be an artifact of providing males with a surplus of high quality nest sites. Alatalo and Lundberg (1984) rejected this hypothesis for Pied Flycatchers by showing that similar proportions of males in areas with and without nest boxes attempted to attract second mates. In contrast, Petit (1991) reported that in the natural situation male Prothonotary Warblers very rarely have access to more than one natural nest cavity and polygyny is extremely rare. She too suggested that polygyny may occur much more frequently in this species when males have a surplus of nest boxes because females are "evolutionarily naive" to the costs of polygyny. This hypothesis was not considered in the other studies cited above with the exception of Marks et al. (1989; see also Korpimiiki 1991:44). The purpose of this study was to determine whether the occurrence of polygyny among box-nesting House Wrens was an artifact of allowing males access to more than one nest box per territory. We asked if and how frequently in the natural situation female House Wrens pair polygynously, and how frequently paired males attempt to attract second mates. We compare these data to similar data gathered when we provided each male with several boxes per territory. Because the frequency of polygyny has not been documented for any naturally-nesting population of House Wrens, we felt that this study was critical prior to testing formal models for the occurrence of polygyny in this species.

Ash-throated Flycatchers (Myiarchus cinerascens) and Mountain Bluebirds (Sialia currucoides) are secondary cavity-nesters that are sympatric in juniper woodlands of northern Nevada. While conducting a study of Mountain Bluebird reproductive strategies during the 1988-1989 breeding seasons, we observed two instances of Ash-throated Flycatchers raising bluebird nestlings in addition to their own young. Our study area is located in partially burned juniper woodlands north of Reno, Nevada, and contains 68 nestboxes. These boxes have been used since 1985 by Mountain Bluebirds and are also used occasionally by Ash-throated Flycatchers. In the first incident, a nestbox which contained two bluebird eggs on 30 May 1989 was taken over by Ashthroated Flycatchers. The adult bluebirds were unbanded, so we are not sure what happened to them after losing the nestbox; they did not use the nestbox again that season. The female flycatcher did little additional nestbuilding (flycatchers in this area use clumps of fur for nest material whereas bluebirds mainly use strips of bark), but laid her clutch of five eggs alongside the two bluebird eggs by 6 June. She incubated the mixed clutch, and all seven eggs hatched on approximately 19 June. In the four times we checked the nest between hatching and 3 July, the rate of nestling development appeared to be equal for both species. Only flycatchers were seen feeding the young. All nestlings presumably fledged on 11 July, except for one almost completely feathered bluebird nestling found mummified in the nestbox on 12 July (cause of death unknown). Despite repeated searches, we did not see the young after fledging. In the second incident, an Ash-throated Flycatcher laid two eggs by 22 June 1989 in a nestbox in which a bluebird pair had previously fledged a clutch of four young. On 5 July there was one Mountain Bluebird egg in the nest, along with two additional Ash-throated Flycatcher eggs. The flycatcher incubated all five eggs. On 12 July, we found one bluebird and two flycatcher young along with a dead flycatcher nestling and an unhatched egg. The young were approximately two days old. Again, only flycatchers were seen caring for the young. On 15 July (five days after hatching), the nest contained only two dead young (one flycatcher and one bluebird). The other nestling and the unhatched egg were missing. The adults were not in the area and were not seen again. Since predation is a major cause of bluebird egg and nestling mortality in our study area (unpubl. data), we assume this was the cause of nest failure, though nest abandonment cannot be completely ruled out. To our knowledge, this is the first report of Ashthroated Flycatchers raising the young of any other species. These two cases are qualitatively different, and we consider two possible explanations for them: 1. competition for suitable nest sites, and 2. facultative brood parasitism. Nest site competition. Two lines of evidence suggest that Mountain Bluebirds and Ash-throated Flycatchers compete for suitable nest sites in this study area. First, we know of four takeovers of bluebird nests by flycatchers since 1985 (two in 1986, one in 1987, one in 1989). There have been no reciprocal takeovers by bluebirds, presumably because flycatchers are much ' Received 15 October 1990. Final acceptance 7 December 1990. SHORT COMMUNICATIONS 461

Birds nesting near House Wrens (Troglodytes aedon) risk having their eggs, nestlings, and nests destroyed. Damage by wrens may be reduced in Black-capped Chickadees (Parus atricapillus), Tufted Titmice (P. bicolor), and other parids by concealing eggs under nest material during the laying period, and in sympatric cavity-nesting species by nesting in different habitats from wrens. To test if eggs were protected by covering, prelaying wrens were challenged for 1 day with a set of two boxes placed 1 m from their nest, one with two artificial eggs (miniature marshmallows) lightly covered under fur, the other with two artificial eggs in an open cup. Results varied with stage of nest-building; in 41 trials where both exposed eggs were removed, covered eggs remained in only 4 of 15 (27%) trials near early nests containing few sticks, but in 17 of 26 (65%) trials near more advanced nests. To assess effects of nest site, a box with a cup nest was placed in each of three habitats 10 or 20 m from 29 wren nests. After 1 day of habituation, two artificial eggs were placed in each nest and left exposed for 1 day. Boxes in woodland interiors were less likely than boxes in fields and along edges to be visited by wrens at least once over 2 days (66 vs. 97% visited) and were less likely to have eggs removed (10 vs. 83% removed). Competitors for nesting cavities also may escape attacks by wrens through differences in breeding period, active defense of territories or nests, or renesting.

Intraspecific brood parasitism occurs frequently among Wood Duck (Aix sponsa) populations nesting in artificial structures. To assess the effects of such parasitism on population ecology, we analyzed 12 years of Wood Duck nesting records (1976-1987) from a study site in northeastern Illinois. Hatchability of eggs (ducklings produced/total eggs laid) was inversely correlated with population density, with the frequency of parasitism, and with the number of eggs laid per nest. The hatchability of all eggs laid in nests that had been parasitized (16-44 eggs) was 57.5% vs. 67.3% for eggs laid in "normal" nests (7-15 eggs). The negative consequences of parasitism were due mainly to nest abandonment, damaged eggs, and eggs laid after the start of incubation, and occurred despite the consistent availability of suitable unused boxes. The frequency of brood parasitism was strongly affected by box placement. During 19761987, parasitism occurred in 49.5% of boxes erected singly in highly visible locations, in 49.5% of boxes erected in highly visible groups, but in only 29.8% of boxes that had been erected singly in visually occluded habitat. Mean clutch sizes for the visible-isolated (15.7 eggs) and visible-clumped (16.3 eggs) boxes were significantly higher (F = 4.49, P = 0.012) than for the well-hidden boxes (12.4 eggs). Hatchability in successful well-hidden nests was 82.0% vs. ca. 74.0% in successful visible boxes. The data suggest that reduced parasitism and increased hatchability occur when artificial nesting structures are placed in habitats and at densities resembling the natural circumstances in which Wood Ducks evolved. These results have implications not only for the study and management of A. sponsa populations, but also for the placement of nest boxes in behavioral and ecological studies of other cavitynesting birds.

The White-bellied Wren (Nannorchilus leucoguster) is a small, plainly colored, almost exclusively Mexican wren which is far more often heard than seen. It is smaller than the House Wren (Troglodytes agdon) and is brownish gray above and grayish white below, and has a fairly distinct grayish white superciliary line. Its wings and tail are faintly barred with dark brown. Its most distinctive feature is its stubby tail, which is only a little more than an inch long. In the Gomez Farias district of southwestern Tamaulipas, where I first encountered this wren in early March of 1938 (Sutton and Burleigh, 1939:36), it lives principally in the thickets of kuipilca or wild pineapple (Bromelia pinguin) , a tough, barbed xerophyte which grows in dense, waist-high mats throughout the brushy woodlands bordering the rivers as well as on the lower foothills of the Sierra Madre Oriental. Here the bird spends much of its time close to the ground, feeding at the bases of theleaf-rosettes, keeping itself more or less hidden even while singing. Its song, a tinkling, ebullient pret-til-ly, pret-til-ly, pret-til-ly, is instantly recognizable as a wren’s because of its rhythmic quality. As the bird sings it lifts its head, but ordinarily it does not assume the head-straight-up, tail-straight-down posture which is characteristic of so many wrens. Two other bird species, the Cinnamomeous Tinamou (Crypturellus cinnumomeus) and Olive Sparrow (Arremonops rujivirgatus), inhabit the huipilla beds with it in that region. .

Most avian brood parasites reproduce by laying eggs in nests of other species (e.g., Hamilton and Orians 1965, Payne 1977), but some may lay in nests of conspecifics. Intraspecific brood parasitism has been reported for over 50 species of birds, mostly ducks (YomTov 1980). For passerines, however, intraspecific brood parasitism has been reported far less frequently, although several well-documented cases do exist (see Yom-Tov et al. 1974, Manwell and Baker 1975). In this note we provide the first evidence for intraspecific brood parasitism in a small, cavity-nesting passerine, the House Wren, Troglodytes aedon. Between 1984 and 1987 we conducted a study of the House Wren breeding ecology in Presqu'ille Provincial Park (hereafter the Park) and in the Mer Bleue Bog (hereafter the Bog) near Ottawa, Ontario (description of these study sites can be found elsewhere; Belles-Isles and Picman 1986a, Belles-Isles 1987). In the 4 years of this study we have made observations on a total of 123 nests and obtained evidence for five probable cases (about 4% of the total) of intraspecific parasitic egg laying. Because we could find no previous reports of intraspecific brood parasitism for this species, below we provide a description of these cases. Cases 1, 2, and 3-Appearance of two eggs per day. First, late in June 1985, we found a nest in the Park, where three eggs were laid in two consecutive days. The final clutch laid in this nest consisted of seven eggs and of these six young fledged. Second, in 1986 in the Bog we recorded a case where the first egg was laid on 22 June, and 4 days later (on 26 June) the nest contained six eggs. The further breeding history of this nest is not known. Third, in one House Wren nest that was under observation in the Bog, six eggs were laid between 16 June and 19 June 1987. This nest successfully fledged all six young. Since passerines normally lay only one egg per day, the appearance of more than one egg per day can be used as evidence for parasitic laying (see Yom-Tov 1980). Case 4-Appearance of a new egg after completion of the clutch. In May/June 1986, we observed the irregular appearance of an egg in a House Wren nest located in the Bog. In this nest seven eggs were laid between 20 and 26 May. During the next visit on 31 May the nest still contained seven eggs. However, on 2 June, we discovered a new egg near the entrance of the nest box. This nest eventually fledged seven young. The irregular time interval between laying of the seventh egg and the last egg, along with an unusual location of the last egg at the box entrance away from the nest depression, strongly suggest that the last egg was laid by a parasitic female. Case 5-Abnormally large clutch. On 25 June 1987, in one of the boxes used for breeding by House Wrens in the Bog, we found a clutch consisting of nine eggs. Most House Wrens in our study areas, however, laid between four and seven eggs (for 1984 to 1987 mean clutch size ? 99% CI = 6.1 ? 0.2; n = 123). The abnormally large clutch in this case thus suggests parasitic laying by another female. The five above cases provide strong evidence for intraspecific nest parasitism in the House Wren, although this mode of reproduction appears to be infrequent (about 4%) in our wren populations. However, ' Received 28 October 1987. Final acceptance 4 January 1988. 2 Present address: Departement de Biologie, Universite Laval, St. Foy, Quebec GIK 7P4, Canada. SHORT COMMUNICATIONS 513

Avian adult infanticide (the killing of conspecific young by an adult) has been reported for several species (e.g., Crook and Shields 1985, Loftin and Roberson 1983, Trail et al. 1981). Here we document one case of attempted infanticide and circumstantial evidence for 3 more cases of infanticide in the European Starling (Sturnus vulgaris). These observations were made during an ongoing study of the behavioral ecology of the starling in Piscataway, New Jersey (Power et al. 1981), from 1983 to 1985. Nest boxes were attached to utility poles found along roads and mowed fields. As part of our studies on intraspecific brood parasitism, boxes were censused daily during laying. Adults were captured after all their eggs hatched and marked with numbered U.S. Fish and Wildlife Service bands and unique combinations of color bands. On 10 May 1984, we banded the breeding female at nest box 1-18. On 11 May 1984, we banded the breeding male and again saw the banded female. This pair had three, five-day-old nestlings. Minutes after the male was banded and released at 16:30, we observed an unbanded female fly to the nest box top (starlings can be sexed from a distance by polymorphism in bill color [Bullough 1942]). She entered the nest box, looked out ofthe entrance hole several times, and then exited to the ground with something in her mouth which she attempted, but failed to eat. (We later found this object to be a fragment of an unhatched egg with dried remains of an embryo.) She then reentered the box, exited quickly, and flew out of sight at 16:40. The breeding adults at this box were not present during this time. As soon as the unmarked female left, we examined the chicks and found that one nestling had a fresh bloody wound near the auditory opening but appeared otherwise healthy; the other two nestlings were unharmed. We examined the contents of the box during the capture of the adult male at 16:30 and observed no irregularities. Therefore, we conclude that the wound was inflicted by the visiting female between 16:30 and 16:40. On 18 May 1984, at box 1-20 a twelve-day-old nestling was discovered with a wound similar to that of the chick in box 1-18, about 80 m away. This wound had to have been inflicted one or more days earlier because the eye nearest to the damaged ear was swollen and infected. Unlike the first nestling described, this nestling died. On 8 June 1983, a dead chick about five days old was found on the ground between two nest boxes, I-13 and I14, with a bad wound over its left eye. This chick was too young to have fledged or even crawled out of its nest. Moreover, no chicks were missing from any of our boxes so this chick must have been carried some distance from its nest. On 5 June 1985, we found a dead four-day-old chick at box 111-12. The area below the chick's left auditory opening was covered with blood. This chick's nestmates had already died by 4 June of apparent starvation. Their mother was banded on 3 June. A male was never captured at this box. On 6 June, an unbanded female was captured in the box and fresh nesting material was present in the nest cup. This female began laying on 12 June. In all cases, the nature of the wound was the same: a peck mark near one of the auditory openings. Similar wounds have been reported by Crook and Shields (1985), Shelley (1934), and Stacey and Edwards (1983) in the context of infanticide. The possibility that mammals or different bird species may have caused the wounds in the three cases for which we have evidence for infanticide seems remote. The only other bird that has ever been observed to enter one of our starling boxes was an American Kestrel (Falco sparverius); it was successfully repelled by the adults at that box. To discourage mammalian predators such as Raccoons (Procyon lotor) and Gray Squirrels (Sciurus carolinensis), aluminum predator guards have been placed around utility poles below nest boxes. Squirrels still occasionally present a problem. However, they always remove the entire contents of the nest (either eggs or nestlings) and disrupt the nest itself. In addition, similar peck marks have been found around the head and neck of dead adults (n = 3) found in nest boxes, and on the faces of pairs of birds that we have captured fighting inside boxes (n = 8 pairs), suggesting that bill stabbing is not uncommon. In two of the four cases, a female was suspected to have committed an infanticidal act. We suspect that infanticide in our population is related to competition for nest sites, a limiting resource (e.g., see Hrdy 1979). Other reports of female infanticidal behavior have been reported by Loftin and Roberson (1983), and Picman (1977). In both cases, a limiting resource (such as nests, mates or food) has been suggested as a reason for infanticidal acts. The importance and frequency of avian infanticide is largely unknown primarily because the observation time necessary to document this phenomenon can be prohibitive. As a result, infanticide may have greater biological significance than is implied by the existing literature. We encourage all observers to be cognizant of the possibility of infanticide in their study populations.

Balgooyen (1976), in his Sierra Nevada study, showed that nest cavities of American Kestrels (Falco sparverius) face east significantly more often than expected, and that nest trees are most often located on east-facing slopes. He based his results on comparisons of observed frequency distributions to a uniform distribution. But American Kestrels, typical of most secondary cavity-nesting birds, use abandoned nest cavities excavated by woodpeckers. It is possible, therefore, that the nonrandom orientations of kestrel nest cavities and slope exposure reflect selection by the original nest excavators rather than by the kestrels. Some studies have reported nonrandom orientations of woodpecker nest cavities (Lawrence 1967, Conner 1975, Inouye 1976, Korol and Hutto 1984). If most available cavities or slopes faced east, the apparent preference by kestrels could be random selection of available cavities or trees. To test this possibility, I compared Balgooyen's (1976) data on nest orientation to an independent sample of 105 nests of the two species whose nests kestrels most often use in California-Northern Flicker (Colaptes auratus) and Lewis' Woodpecker (Melanerpes lewis; Raphael and White 1984). I collected data from 1975 to 1978 on the same study areas reported by Balgooyen (1976). My null hypotheses were that: (1) no difference existed in orientation of kestrel nest cavities compared to that of available cavities, and (2) slope exposures were equal for kestrel nest trees and available trees. I tested the hypotheses using Watson's U2 test (Batschelet 1965:35). Both hypotheses were rejected. Nest cavity orientation differed significantly from expected (U2105,58 = 0.307, P < 0.005), and slope exposures also differed from expected (U293,58 = 0.490, P < 0.005; Table 1). Available cavities were generally oriented in a northerly direction (mean azimuth = 14*; Table 1), whereas most kestrel cavities faced east-northeastward (mean angle = 59*). Angular dispersions, which measure the relative concentration of points around the mean, were similar among nests and available trees for both cavity orientation and slope exposure (Table 1). Examination of differences between percentages of kestrel and woodpecker nests for each of the eight directions showed the greatest deviation for east-facing cavities and slopes (Table 1), supporting Balgooyen's original observations. Balgooyen (1976) speculated that nest cavities facing eastward might offer thermoregulatory advantages because of warmth of the morning sun and protection from storms and hot afternoon temperatures. These considerations should also apply to the woodpeckers that excavated the nests. If so, most woodpecker nests should have been excavated with east exposures. It is possible that woodpe kers excavated cavities at the place around t e tru k where decay conditions were best for nest excavation. In the present study area, however, both Lewis' Woodpecke s and Northern Flickers excavated nests in trees that were decayed throughout (Raphael and White 1984). Therefore, it is unlikely that their nests were oriented in relation to variable decay characteristics of the trees. While these results do not rule out the possibility that kestrels choose cavities to maximize thermal advantages, further study would be necessary before accepting such an explanation. The apparently nonrandom selection of east-facing cavities by kestrels nevertheless cannot be attributed to cavity availability.

Les relations entre la structure de l'habitat,le choix du site de nidification et l'issue de la reproduction de Troglodytes aedon dans des forets ripicoles du Wyoming

Attendants are common at Tree Swallow (Tachycineta bicolor) nests during the nestling period. Parent-attendant interactions were studied at a Tree Swallow nest box trail in New York. Attendants did not cooperate with parents (Lombardo 1986a) and were hypothesized to be individuals in search of potential future nest sites (Lombardo 1987). Therefore, they posed several potential threats to parental reproductive success. Even though parents commonly encountered attendants at their nests, parent-attendant interactions were usually nonhostile. Parents were very unresponsive to model-attendants during the nestling period. Parents infrequently chased live attendants or attacked modelattendants presumably because the potential threats posed by attendants were rarely realized. Attendants were most active late in the breeding season when it was too late for attendants capable of breeding to breed successfully. Hatching year attendants had little to gain by behaving aggressively towards parents. This mutual restraint in conflict could be maintained by reciprocity (Lombardo 1985).

At temperatures below 28”C, rate of oxygen consumption (vjo2) of Zebra Finches (Poephila guttuta) incubating eggs averaged 20% higher than the \ioz of non-incubating Zebra Finches sitting in a nest at the same temperature. This increase represents the energetic cost of incubation. The O,, of non-incubating birds sitting in a nest was lower than values reported for birds perched in the open at the same temperature. In the Zebra Finch, the ameliorating effects of the nest microclimate approximately compensate for the increment in metabolic rate due to incubation. The energetic cost of incubation increased when birds had to rewarm cold eggs. Incubating birds responded to artificially cooled eggs by elevating their metabolic rate and increasing heat flow to the clutch. The pattern of adult attentiveness at the nest determines the number of times and amount by which the eggs must be rewarmed. Because it is energetically more expensive to rewarm eggs than to maintain temperature once the eggs are warm, the cost of incubation depends in part on the attentiveness pattern. Reproduction, especially the care of eggs and young, places special demands on the way birds allocate available energy. Various techniques have been used to estimate the energetic costs associated with territorial defense (Stiles 1971, Wolf and Hainsworth I971), nest building (Collias and Collias 1967, Withers 1977a), egg production (King 1973), and the feeding of nestlings (Utter and Lefebvre 1973). These activities, together with incubation of the eggs, include most of the time and energy that birds devote to reproductive activities. However, the costs of incubation, an activity that takes up a significant portion of the reproductive cycle, are difficult to measure and have been the subject of controversy (Kendeigh 1973, King 1973). Linear heat flow models have been used to make indirect estimates of the energetic cost of incubation based on the assumption that heat loss from eggs must be balanced by extra heat production by the parent (Kendeigh 1963, Ricklefs 1974). For example, Drent (1970) found that Kendeigh’ s (1963) model accurately described the heat input required to keep the eggs of Herring Gulls (Larus urgentu Mertens 1977) and Baird’ s Sandpiper, (Calidris hairi Norton 1973). However, neither author compared the oxygen consumption of incubating and non-incubating birds, and consequently it is impossible to estimate the energy expended solely for incubation. In contrast, Biebach (1977, 1979) measured the oxygen consumption of both incubating and non-incubating Starlings (Sturnus dgaris) and calculated the energetic cost of incubation at several nest temperatures. Gessaman and Findell (1979) measured CO, production of three incubating and non-incubating American Kestrels (F&o sparzjerius) but their results are ambiguous. Mertens (1980) measured heat loss from the nest of a Great Tit, using heat flux disks mounted in the nestbox walls, and found that heat loss from the bird and nest increased considerably during incubation. The energetic cost of warming cooled eggs “to the incubation temperature” has not been determined. Kendeigh et al. (1977) suggested that energy expended to rewarm eggs could be calculated from estimates of the heat needed to rewarm eggs, but this procedure ignores the inefficiency of heat transfer from the parent to the eggs. If a bird increases its heat production in order to re

Birds of several species have been reported to kill immature birds of other species in contexts other than predation. Contexts include: (1) takeover of specialized nesting sites such as cavities (e.g., Kendeigh 1941, Pinkowski 1977), (2) brood parasitism (reviewed by Payne 1977), and (3) elimination of potential competitors for food (suggested by Picman 1977, 1980 for Long-billed Marsh Wrens [Cistothorus palustris]; Belles-Isles and Picman 1986 for temperate House Wrens [Troglodytes aedon]). The latter context is problematical because it cannot be inferred without evidence of actual or potential food limitation. In this note I document interspecific infanticide of tropical House Wrens by Rufousand-White Wrens (Thryothorus rufalbus). The infanticide appears to be based on competition for food since nestlings were killed only during an 8-week food shortage within a 4-year period. The infanticide was detected during a study of House Wrens conducted between 1982 and 1985 near the rural village of La Laguna, Republic of Panama (approximately 25 km northeast of Panama City). Six attacks occurred between 23 May and 14 July 1983; three were observed and three have been inferred (Table 1). On 23 and 24 May, a Rufous-and-White Wren was perched at the entrance of a nest box containing three House Wren nestlings (3 days old on 23 May). The box was mounted on a 1.25 cm diameter pole at a height of 1.6 m. The intruder thrust its head and beak rapidly and repeatedly into the nest and threw out one nestling on the first day. This nestling, as well as one of the remaining nestlings, had lacerations on the head and abdomen and puncture wounds on the abdomen. Thereafter one nestling was missing each day for two days. Parental House Wrens returning to the nest were driven away by the intruder during both days of observation. In a second case, on 9 July, an observer frightened a Rufous-and-White Wren from its perched position at the entrance of the nest box shortly after it commenced thrusting its head repeatedly inside the box. This nest contained six nestlings 10 days old. No mortality or injury resulted from this interrupted attack, and there was no evidence of repeated visits (i.e., no nestling loss or injury) for 3 days, after which a snake ate the nestlings. This second nest was located 3 km from the first, suggesting that two different Rufous-and-White Wrens were responsible for these incidents. In a third case, on 19 June, a Rufous-andWhite Wren repeatedly pecked a House Wren fledgling for 15 sec in a family group of recent fledglings and parents. The fledgling escaped and was observed 5 days later. This incident took place approximately 100 m from the first incident. The House Wren breeding season extended through October of 1983 (approximate length 24 weeks), but no further direct interactions between the two wrens were observed. Three additional nest losses (one partial) between late May and mid-July of 1983 may have been caused by Rufous-and-White Wrens because of similar patterns of lacerations and puncture wounds on the bodies of dead or dying nestlings (Table 1). One nestling had a severely broken tibiotarsus as well. Rufous-and-White Wrens were seen or heard within 25 m of these nests on the day of detection of infanticide. The nests were located at least 1 km apart and between 200 to 1,300 m from the nests mentioned above, suggesting that the Rufous-and-White Wrens seen in the vicinity of these nests were different individuals. Some alternative causes of the infanticide can be eliminated. Predators were probably not responsible for the killings because the dead or dying nestlings were not eaten. Infanticide by other House Wrens, associated with takeovers of mates or territories during each

A male is considered polygynous whenever he forms a prolonged pair bond with two or more females whose nesting cycles overlap in time (Wittenberger 1981). Polygyny is rare in waterfowl (Wittenberger and Tilson 1980, Ford 1983) but commonly occurs in two species, the Magpie Goose Anseranas semipalmata and the Comb Duck Sarkidiornis melanotos (Frith and Davies 1961, Siegfried 1979). Studies of captive birds have indicated that some southern hemisphere dabbling ducks are occasionally polygynous (McKinney and Stolen 1982, Stolen and McKinney 1983, McKinney and Bruggers 1983, McKinney 1985). Similar studies of North American dabbling ducks have not documented polygyny (Stolen and McKinney 1983; McKinney 1985). Among North American diving ducks, polygyny has been reported only in the Canvasback Aythya valisineria (M. Anderson in Ford 1983). Males of Common Goldeneye (Bucephala clangula) and Barrow's Goldeneye (B. islandica) have been observed defending two females, suggesting that polygyny may occur in these species (M. Erickson, pers. comm.; Savard 1985a). In this note, I describe four cases of polygyny observed in 1984 among 229 pairs of Barrow's Goldeneye during a study of territorial behavior in the interior of British Columbia, Canada (Savard 1982). Paired Barrow's Goldeneye drakes defend territories on their breeding ponds until mid-incubation. They exclude all conspecifics except their mate from the territory (Savard 1982). Territorial boundaries are relatively stable during the breeding season as indicated by observation of marked individuals. Unpaired birds are restricted to the center of the ponds by the aggressiveness of territorial males. Such a system facilitates population estimates and also the detection ofpolygyny. The presence of two females within a male's territory would indicate polygyny. Normally strange females are chased off the territory (Savard 1982). Detection of polygyny was further enhanced by the presence of 98 individually marked individuals (13 males, 85 females) in the population. Four counts conducted in early May 1984 yielded an average of 222 ? 3 (SE) pairs for the study area. Case 1. Pair A (female marked with nasal disks) arrived on its breeding pond (Lake 13) on 13 April when 90% of the lake was still covered with ice. By 15 April, two other pairs had joined them. Female B (marked) was first seen on 17 April on the pond and did not seem paired. This was unusual, as unpaired adult females are rarely seen on the breeding areas. On 18 April, Male A was defending a territory from which he excluded all goldeneyes but Females A and B. Three monogamous males also defended territories on the lake, and there were several unpaired males on neighboring ponds. No aggression was observed between Females A and B. Female A started laying on 20 April and Female B on 29 April; each laid eight eggs in the same nest boxes they had used the previous year. Female A started incubation on 3 May and Female B on 17 May. The nest of Female A was destroyed by a black bear (Ursus americanus) on 4 May, whereas that of Female B was deserted on 27 May because of egg predation by American red squirrel (Tamiasciurus hudsonicus). Both females remained with Male A in the territory until his departure on 5 June (Male A had been captured and marked on 13 May). The two females then spent most of their time on Lake 13 associating temporarily with other females but rarely together. They were last seen on 5 July. Both females had been marked in earlier years so that their breeding history was partially known. Female A nested in 1982 and 1983 in the same nest box she had used in 1984 and raised a brood on Lake 13 each year. In 1983 her breeding territory was on Lake 13 and her mate was monogamous. Female B nested in 1983 in the same box she had used in 1984 and also raised a brood on Lake 13. Because no polygynous males were seen in the area in 1983 it is assumed that she was paired with a monogamous male. It is also likely that her mate's territory was also on Lake 13. Case 2. In this case, I witnessed the acquisition of the second female; Pair C (female marked) was first seen on a lake beside their breeding pond at 0500 on 4 April. At 1600, they landed on their breeding pond and challenged an established pair. After a violent fight in which both sexes participated, Pair C took over the territory. On 5, 6 and 7 April, the male was observed defending the territory. There were only two other pairs defending territories in this section of the pond and none adjacent to Pair C. However on 8 April, five pairs were defending small territories, one of which (Pair D) was adjacent to Pair C's territory. At 0645 Pair D copulated. At 0655, Male C attacked Male D (unmarked), and after a violent fight Male D left the pond, abandoning his mate. Male C did not show any aggression toward Female D, but Female C did (threat). At 0710, Male C approached Female D and both displayed to each other (rotary pumping; Palmer 1976). Female C was ignored in the following days as Male C spent more time with Female D. However Male C still defended his original territory and chased all goldeneyes that approached Female C. On 13 April, Female C returned from her nest and landed in her territory. She was greeted by Male C and both did the rotary pumping display. Then Female C twice attacked Female D, who swam away. Female C again threatened Female D, but this time Male C left her and swam to Female D and both did the rotary pumping display and swam away from Female C. I did not witness any further aggression between the females and both remained with Male C. I witnessed two copulations: on 1 May at 0725, Male C copulated with Female C, and Female D swam toward them assuming a prone posture but Male C did not respond; on 6 May at 0901, Male C copulated with Female D. Female C initiated her clutch on 5 May and hatched 14 young. It is not known if Female D nested, but her occasional absence from the territory indicates that she may have attempted to nest. Case 3. A male (G) with two females was observed on 30 April, defending a territory on a small pond that also ' Received 6 June 1985. Final acceptance 4 November 1985.

Despite considerable interest in its occurrence or potential occurrence (e.g., Lorenz 1963), both direct and circumstantial evidence of intraspecific killing in adult passerines is rare (see Davis 1940, Cottrille 1950, Grubbs 1977, Loflin 1982). The purpose of this note is to add to this meager data base by presenting evidence of intraspecific killing in adult Tree Swallows (Tachycineta bicolor). My study site is a nest box colony on the salt marshes of the John F. Kennedy Memorial Wildlife Refuge located adjacent to Tobay Beach on the south shore of Long Island, New York (see Schaeffer 1972 for a description of the study site). On 10 Mav 1983 I discovered two birds. a male and a female in brown second-year plumage (see Dwight 1900, Cohen 1980, Hussell 1983) inside Box 134 during a routine census. The male was on top of the female. I banded both birds with U.S. Fish & Wildlife Service aluminum bands. The box did not contain nesting material. I returned to Box 134 on 14 May 1983 and found the female dead on the floor of the box, flat on her stomach with her wings spread out to her sides. Her head was tilted up and back; her forehead was defeathered and covered with dried blood and puncture wounds. For several reasons, I believe that another Tree Swallow caused these wounds. First, no other species used the nest boxes at my study site. Therefore, Tree Swallows competed only among themselves for these sites, so it is unlikely that an interspecific nest site competitor was responsible for the female’s death. Second, Kuerzi (194 1) presented evidence of intraspecific killing in Tree Swallows and reported two fights between a male and a female in brown plumage. During one fight the brown female had the male pinned on the ground, and she pecked at the back of his head until he escaped when Kuerzi approached for a better view. Kuerzi (1941) also reported that a Tree Swallow killed a female Eastern Bluebird (Sialia siulis). This evidence indicates that Tree Swallows are capable of inflicting mortal wounds on one another. Third, infanticide is known in this species (Shelley 1934). Quinney (1983) attributed the greater disappearance rate of eggs and very young nestlings at polygynous nests relative to monogamous nests to the action of females attempting to prevent other females from using the same nest box in polygynous pairs. In 198 1 I found a dead one-day-old nestling with a puncture wound behind one eye, a type of wound common in victims of avian infanticide (see Mock 1984; Crook and Shields, 1985). Last, in an experiment to determine the

Description d'observations concernant l'utilisation de nichoirs artificiels comme perchoirs nocturnes chez l'etourneau europeen et examen de son implication dans la competition pour les sites de nidification

Nest site selection was analyzed for a Mountain Bluebird (Sialia currucoides) population using two different types of nest box in southcentral Washington. The majority of adult females successful in fledging young during the previous year either returned to the same territory and nest box or selected the same type of nest box if they changed territories. If they were unsuccessful, adult females tended to change territories and box types. Most male and female bluebirds breeding for the first time selected the same type of box as housed their natal nest even though none of these birds returned to its natal territory. Nest site selection and breeding area fidelity were influenced by age, sex, previous breeding experience, and natal nest type. Recently, Cink (1976) examined the degree to which nestling House Sparrows (Passer domesticus) imprinted on the type of structure housing their natal nest. Although he found no evidence that early learning or imprinting had any effect on nest site selection, females tended to choose hole-type nests over open nests. Other studies have shown that some species prefer a larger to a smaller nest box (Jiirvinen 1978) and that floor dimensions of a box can influence clutch size (Karlsson and Nilsson 1977). Jackson and Tate (1974) analyzed selection of artificial nest sites by Purple Martins (Progne subis), House Sparrows, and Starlings (Sturnus vulgaris) and found only slight differences related to interior and exterior colors, location, and materials from which the boxes were constructed. Lumsden (1976) reported that Starlings preferred small entrance holes and dark interiors. Bluebirds, like all cavity-nesting species, are limited by availability of suitable nest sites. Many studies (e.g., Miller 1970, Power 1974) have shown that bluebird populations can be increased by placement of nest boxes in suitable habitat. Although much is known about the reproductive biology of bluebird populations (Power 1966, Peakall 1970, White and Woolfenden 1973, Pinkowski 1977a, 1979a), little has been published concerning nest box selection and breeding area fidelity (the tendency for birds to return to the territory used the previous breeding season). Pinkowski (1979b) analyzed breeding data for Eastern Bluebirds (Sialia sialis) using artificial and natural nest cavities and found that age and nesting success seemed to be the most important factors influencing nest site selection. Additionally, he concluded that imprinting on the natal type of nest site was not important. I theorized that imprinting on the natal type of nest site would be important for secondary cavity-nesting species because of the scarcity of natural cavities and that species-specific differences could influence nest site selection. To test these theories, I examined breeding data for a Mountain Bluebird (Sialia currucoides) population using two different types of nest box and analyzed the influences of age, sex, previous breeding experience, and natal nest type on nest site selection. STUDY AREA AND METHODS The study area was located south of Bickleton and Cleveland, Klickitat County, Washington. Elevation ranges from 915 m near Bickleton on the north to 701 m in valleys running north-south. The northern edge of the study area is on the ecotone between ponderosa pine-Oregon white oak (Pinus ponderosa-Quercus garryana) forest and big sagebrush-bluebunch wheatgrass (Artemisia tridentata-Agropyron spicatum) steppe. Much of the land south of Bickleton and Cleveland is farmed with winter and spring wheat and with barley. Areas not cultivated are moderately grazed by cattle. The two types of nest box were designated as either "old" or "new" indicating how long they had been present on the study area. The "old" boxes were first erected in 1966 and new boxes were added each year (J. Brinkerhoff, pers. comm.). These boxes resembled a small house with a peaked roof. The inside dimensions of the floor were 30 x 15 cm with an entrance hole diameter of 4.4 cm; the entrance hole was approximately 10 cm above the floor. The outside of these boxes had a blue roof and white sides; the interiors were not painted. All of the "new" boxes had inside floor dimensions of 12.7 x 12.7 cm with a 3.8-cm diameter entrance hole, the bottom of which was 14 cm from the floor. The "new" boxes were not painted. Both "old" and "new" boxes were made of wood. The number of "old" box types available was usually 50 (except for 41 in 1976) and "new" box types numbered 30-31. "Old" type boxes were placed on top of wooden fence posts and "new" type boxes were nailed to the

down on both our visits. Breckenridge (op. cit.), however, doubts the importance of down as insulation for Wood Duck eggs during periods when the hen is absent. Fourth, Wood Ducks' ducklings leave the nest in response to auditory cues learned during the brooding period immediately after hatching (Gottlieb, J. Comp. Phys. Psych. 56:86-91, 1963). Similar behavior undoubtedly prompts the departure of young Tree Ducks, but this, too, remains conjectural. Nonetheless, the entire brood of both species left the nesting box, suggesting that the cues for departure may not be species-specific in cavity-nesting waterfowl. The survival value for all cavity-nesting ducklings which hatch i a host-parasite situation seems obvious. Weller (op. cit.) should be consulted for a full listing of interspeciflc egg parasitism among waterfowl, including cavity-nesting species. We ar indebte to Clarence Cottam for his review of this manuscript, and to the United States Fish and Wildlife Service and to the Caeser Kleberg Wildlife Foundation fo their financial support of the senior and junior authors, respectively, during the summer of 1967.