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In species with biparental care, coordination of parental activities can have important fitness consequences. However, specific behavioral mechanism allowing the coordination of breeding partners remains largely unexplored. Prevalence of biparental care in seabirds makes this group particularly interesting for investigation of behavioral underpinnings of parental coordination. Here, we examined vocal behavior at the nest site of breeding partners and its role in shaping their parental share during incubation in the little auk (Alle alle). We evaluated two hypotheses related to the mechanisms involved in parental coordination: (1) behavioral adjustment, where a parent adjusts its effort according to the preceding effort of its partner and (2) vocal negotiation, where effort is adjusted based on information exchanged during the preceding vocal interaction. We found that little auk partners equally share their incubation time, although, duration of nest attendance is highly variable. No immediate reciprocity between partners in the time allocated to parental activity was observed as predicted by behavioral adjustment. However, nest attendance appeared to be related to the vocal interaction between partners during turn-taking. The duration of a given attendance was positively associated to the pair's vocal activity and amount of vocal overlap occurring during turn-taking at the nest. Our results suggest a role of vocalization for coordinating between breeding pairs, providing a potential mechanism for the communication of information enabling this complex interaction. [ABSTRACT FROM AUTHOR]

Conditions encountered during early development affect future survival and reproduction in many bird species. For parents, it is important what body condition the nestlings will achieve at fledging because the condition affects the offspring's chances to survive and reproduce in the future. However, there is a trade-off between the number of nestlings and their condition. We studied parental behaviour and nestling body condition in uniparental Penduline Tits. In this small passerine, the parental care (incubation and food provisioning) is provided by the female only (49% of clutches in the study population) or the male only (15%). In addition, over a third of clutches are deserted by both parents before the start of incubation. We found that female-only cared clutches had more eggs and nestlings and produced more fledglings than male-only cared clutches. The incubation behaviour and incubation temperature in both types of clutches were similar. The provisioning rate per brood was positively, and the provisioning rate per nestling was negatively, correlated with brood size. Although males cared for smaller clutches, parent sex was not significant in both models of provisioning rates (per brood and per nestling). Moreover, the provisioning rate did not predict the brood's average nestling condition. However, nestlings reared in broods with male care were in better condition than those reared by females. At the age of 13 days, they had a higher scaled mass index (describes the relative size of energy reserves) and higher haemoglobin levels. The results suggest that the lower productivity of male-only cared clutches, compared to those cared for only by females, may be compensated by the higher condition of nestlings. Information about the recruitment success of broods cared for by males and females will be necessary to test this prediction. [ABSTRACT FROM AUTHOR]

Offspring desertion by a single parent, mainly the female, occurs in many charadriiform birds. According to the differential parental capacity hypothesis (DPCH), females are more likely to desert, since they may be in poorer body condition than males as a consequence of egg-laying costs. This study investigated the body condition of 122 male and 118 female Whiskered Terns. In this species half of females desert during the chick-rearing period, the remainder during the post-fledging period. Body condition was investigated during the late incubation and early chick-rearing phases during the biparental care period in: (1) females that deserted during the chick-rearing period, (2) females that did not desert during this time, (3) males deserted by females, and (4) males not deserted by females. Among females that stayed, body condition during the pre-hatching period did not vary with relative catching date (clutch/brood age), whereas females that later deserted showed a very poor body condition when caught around seven days prior to hatching. After hatching, body condition was lower in both deserting and non-deserting females caught later. Among males whose females stayed, body condition remained nearly stable, whereas the body condition of males whose females deserted was lower the later they were caught. These results tally only partially with the DPCH: the pattern of parental body condition changes during breeding is apparently more complex than assumed by the DPCH and the cost of egg laying may be lower than suggested. Desertion by Whiskered Tern females is better explained by the sex role differences in parental care. The male's ability to compensate for the missing female may be playing a role in the evolution of desertion. [ABSTRACT FROM AUTHOR]

In biparental Charadriinae plovers, male and female incubation duties often resemble daily routines, with males typically incubating at night and females incubating during the day. By analysing incubation behaviour in three Arctic populations of Common Ringed Plover Charadrius hiaticula, we show that these diel routines are lost in the 24-h sunlight of the Arctic. In contrast, a non-Arctic population in East Scotland exhibited significant daily routines, with males dominating incubation during the late afternoon and night, and females dominating incubation during the early morning and midday hours. These patterns suggest that clear light/dark cycles are necessary for daily incubation routines to form in the Common Ringed Plover, although further research is needed to understand the specific drivers of this behaviour. [ABSTRACT FROM AUTHOR]

In the Galapagos Islands, many endemic landbird populations are declining due to habitat degradation, food availability, introduced species and other factors. Given nestlings typically lack efficient defense mechanisms against parasites, hematophagous ectoparasites such as the larvae of the introduced Avian Vampire Fly, Philornis downsi, can impose high brood mortality and cause threatening population declines in Darwin finches and other landbirds. Here, we assess whether the food compensation hypothesis (i.e., the parents' potential to compensate for deleterious parasite effects via increased food provisioning) applies to the Green Warbler-Finch. We differentiated nests with low or high infestation levels by P. downsi and quantified food provisioning rates of male and female parents, time females spent brooding nestlings, and nestling growth. Male provisioning rates, total provisioning rates and female brooding time did not significantly vary in relation to infestation levels, nor by the number of nestlings. Opposed to the predictions of the food compensation hypothesis, females showed significantly reduced provisioning rates at high infestation levels. Nestling body mass was significantly lower and there was a reduction of skeletal growth, although not significantly, in highly infested nests. The females' response to high infestation may be due to parasites directly attacking and weakening brooding females, or else that females actively reduce current reproductive effort in favor of future reproduction. This life-history trade-off may be typical for Darwin finches and many tropical birds with long lifespans and therefore high residual reproductive value. Conservation strategies may not build on the potential for parental food compensation by this species. [ABSTRACT FROM AUTHOR]

Several hypotheses propose an adaptive function of non-breeding nests (female attraction, decoys for nest predators and safe places for roosting). Alternatively, non-breeding nests may be structures abandoned before completion. Grass Wrens Cistothorus platensis build two types of non-breeding nests: platform and dummy nests. Platforms are rudimentary accumulations of grasses whilst dummies are dome-shaped, similar in appearance to breeding nests. We assess nest ontogeny, structure, dimensions and placement of non-breeding and breeding nests to provide evidence of abandonment. We predict that non-breeding nests would lack several of the nest layers present in breeding nests but would not differ in nesting microhabitat. Platforms had an incomplete structural layer and lacked most of the functional layers present in the breeding nests. Dummy nests had a complete structural layer, but often lacked some of the layers (lining and nest cup) that were added during the later stages of building. Breeding and non-breeding nests did not differ in seven nesting microhabitat variables. These results are in line with the hypothesis that platforms and dummy nests are structures abandoned during the building process. Differences between non-breeding and breeding nests in both nest and entrance orientation suggest that nests with an NNE orientation were less likely to be abandoned. Hence, wrens may abandon nests if they perceive unsuitable ambient conditions at the nest site. However, other causes of desertion such as the encounter of a predator during building were not evaluated. The study of non-breeding nests may provide the opportunity to evaluate the costs and benefits of nest desertion as well as insights in how function can shape nest architecture and location. [ABSTRACT FROM AUTHOR]

Nest care and brooding in sunbirds (Nectariniidae) is thought to be performed exclusively by females. Here, we provide the first evidence that male sunbirds might help with brooding. During a ringing session in Hoekwil, South Africa, we observed one male Amethyst Sunbird (Chalcomitra amethystina) with a brood patch. Its sex was confirmed using molecular methods, and our observation suggests that nest care in sunbirds may at least in some cases be biparental. [ABSTRACT FROM AUTHOR]

Patterns of extra pair paternity (EPP) and intraspecific brood parasitism (IBP) were studied in a Whiskered Tern Chlidonias hybrida population characterized by female brood desertion, a high level of extra pair courtship feedings (10%) and a low level of extra pair copulation (EPC; 0.6%). In this study, we used a set of microsatellite loci to analyse parentage in 56 Whiskered Tern families from southern Poland. Depending on the method, we detected that 1.4%–3.6% of chicks were sired by an extra-pair male, and extra-pair chicks were present in 3.6%–8.9% of broods. IBP was observed in 8.9%–14.3% of broods, corresponding to 3.6%–6.4% of the chicks. The low rate of EPP is in agreement with the hypothesis that in species with high male parental investment, females should avoid EPC. The low level of IBP indicates that intraspecific egg dumping is not a common female strategy in Whiskered Tern, similar to many other colonial waterbird species. [ABSTRACT FROM AUTHOR]

Ambient temperature experienced by an animal during development or subsequently as an adult can affect many aspects of its behaviour and life-history traits. In birds, egg incubation is a vital component of reproduction and parental care. Several studies have suggested that environmental factors (such as nest microclimate) can influence the ability of incubating parents to maintain suitable conditions for embryo development. Here, we manipulated the developmental conditions of embryos through a modification of nest box thermal microclimate to investigate female incubation behaviour and its impact on offspring fitness-related traits in a wild population of the Collared Flycatcher (Ficedula albicollis). The temperature in experimental nests was increased using a heat-pack placed under the roof of a nest box, resulting in an average temperature increase of 2.5 ºC, which corresponds to projected climate change scenarios. We demonstrated that females from nests with elevated temperature spent less time in the nest box during egg incubation and had more off-bouts than females from control nests. Moreover, we found that offspring from the experimentally heated nests had larger body mass at fledging in comparison to the control ones. Our study indicates that nest microclimate during the incubation period affects female incubation behaviour and offspring quality, indicating that environmental variation in nest temperature early in ontogeny can have important and long-lasting fitness consequences. [ABSTRACT FROM AUTHOR]

Parental care is defined as any behavioral trait of the parents that improves the fitness of the offspring, and that probably evolved or is currently maintained by this function. There is variation in the type and amount of care allocated by parents depending on fluctuation in brood demands that respond to growth and developmental environment. Each sex, within the breeding pair, may respond differently to changing brood demands, and such variation might impact offspring development and fitness. Even though there is a plethora of studies evaluating sex differences in parental care, proximate factors influencing distribution of parental duties within the breeding pairs have received far less attention. In a wild population of Western Bluebirds, we assessed sex differences in parental care (i.e. brood attendance, food deliveries, nest cleaning) through nestling development, and evaluated whether distribution of parental care between sexes is associated with offspring growth. We found that females adjusted their parental behavior according to changes in brood demands more often than males, and fed, attended, and cleaned more than males. Moreover, a more female-biased distribution of care through nestling development was positively associated with the growth of fledglings. We conclude that sex differences in parental care may be a measure of specialization in parental duties within breeding pairs favored by natural selection. These findings are in marked contrast to earlier studies in Northern populations of Western Bluebirds that have failed to detect differences in parental care between sexes, and suggest that differences in the social environment or ecological conditions between populations of the same species might lead to differences in parental cooperation between males and females. [ABSTRACT FROM AUTHOR]

Interspecific brood parasites exploit the parental care of host species. This exploitation entails fitness costs for the hosts, which favor the evolution of antiparasitic defenses. Host defenses select for counter-defenses in the parasite, which in turn select for improved host defenses; this results in a coevolutionary arms race that may operate at each stage of the nesting cycle of the host. Most studied examples of the coevolutionary arms race in brood parasites are restricted to the egg stage, with relatively few studies showing coevolution between hosts and parasites at the nestling or fledgling stages; studies on the whole set of host defenses and potential parasite counter-defenses at each stage of the breeding cycle are still lacking. Systems in which parasites are host specialists are particularly well suited to an examination of the pairwise coevolutionary interactions before, during and after host egg-laying, and how these interactions have shaped host resistance or tolerance of parasitism. The Screaming Cowbird (Molothrus rufoaxillaris) is one of the most specialized brood parasites, and mainly parasitizes nests of a single host species, the Grayish Baywing (Agelaioides badius). Parasitism rates of Grayish Baywing nests are extremely high, with most nests parasitized several times. Several traits of this host-parasite system suggest ancient coevolutionary relationships encompassing the entire nesting cycle. In this paper we summarize the main results of a long-term study on the costs of Screaming Cowbird parasitism on the Grayish Baywing's reproductive success and how these costs have favored reciprocal adaptations and counter-adaptations at each stage of the nesting cycle. [ABSTRACT FROM AUTHOR]

Shorebirds (sandpipers, plovers and allies) are some of the most charismatic animals that breed on all continents and inhabit diverse habitats, and their ecology, behaviour and evolution have attracted much attention ever since the work of Charles Darwin. Here I summarise the insights from 30 years of research on shorebird biology to illustrate the contributions of these to four research fields: breeding system evolution, sex ratio research, speciation and biodiversity conservation. Two major conclusions can be drawn from these insights. First, as shorebirds live in a variety of habitats and exhibit puzzling adaptations to their environments, studying their ecology, behaviour and life histories provides novel insights into the emergence and maintenance of organismal diversity. Second, to uncover patterns and processes in evolution, it is both important and stimulating to combine different research methods, and detailed single-species studies with multi-species comparative approach. My main thesis is that curiosity-driven research into the natural history of non-conventional model organisms provides novel insights into fundamental processes in ecology, behaviour and evolution. I also argue that scientific funding should follow the Goldilocks principle: not too little, not too much, just the right amount. [ABSTRACT FROM AUTHOR]

In species where the offspring are naturally deserted by one parent, the experimental stressing of breeding individuals can provide valuable information on the mechanisms underlying desertions and thus the evolution of parental roles. During a study conducted in southern Poland in 2016 and 2017, we investigated factors influencing desertion during the chick-rearing period by male and female Whiskered Terns Chlidonias hybrida (a species in which female desertion occurs) subjected to acute stress. We predicted that stressed females should desert their broods at a higher rate than males because of their smaller contribution to chick feeding and the probable lower cost of female desertion. For the control nests, we released birds immediately after trapping, whereas in the treatment group we temporarily removed birds from their nests, releasing them 9 or 24 h after being trapped. Birds deserted significantly more often in the treatment (28%) than in the control (7%) nests. The response to stress depended strongly on the sex-body condition interaction: in males, the probability of return to the nest after release was high and unrelated to condition, while in females the probability of return increased with body condition in both the treatment and the control groups. Breeding success in both categories of nests was not related to desertion or any of the other factors studied. This study suggests that in species where females naturally tend to desert, desertion by females subjected to disturbance may be associated with the level of their body reserves, whereas males desert at a low rate, irrespective of their body condition. More importantly, body condition appears to be an important factor that influences natural desertion. [ABSTRACT FROM AUTHOR]

Seabirds are long-lived birds that invest in offspring at very high levels, for which male parental care is indispensable. These characteristics are thought to explain seabirds' generally low level of extra-pair paternity (EPP). Although the Streaked Shearwater (Calonectris leucomelas) is a socially monogamous seabird, it is known to copulate outside its social pair bond, which implies the frequent occurrence of EPP. In the closely related Cory's Shearwater Calonectris borealis, cuckoldry is related to body size of the social male. To determine whether body-size-related EPP occurs among Streaked Shearwaters, we established 39 new microsatellite markers for parentage analysis and compared body size between cuckolded and non-cuckolded males. With the new markers, we found that extra-pair males sired 17 (15.0%) of 113 offspring during the 2014-2016 study period, which included three 1.5-month chick-rearing periods. This percentage is among the highest recorded for seabirds. We also found the bill and wing length of cuckolded males to be significantly shorter than those of non-cuckolded males, and that females can reject attempted copulations. These observations imply that EPP in this species is size related and involves female acceptance. [ABSTRACT FROM AUTHOR]

Several studies have found that adult birds of altricial species adjust their parental care behaviour (i.e. nest visits) in response to the current risk of predation for their offspring. However, no experimental study has so far investigated whether there are sex differences in these passive anti-predator responses during the nestling period. Differences between males and females could arise because of several factors, including (1) probability of detection, (2) confidence in parenthood, and (3) different parental care behaviour associated with each sex. To test whether these anti-predator passive responses involve sex differences, we experimentally manipulated the perceived risk of nest predation of adult Common Blackbirds ( Turdus merula), a sexually dimorphic species with a relatively high extra-pair paternity level. Our results showed that nest predation significantly reduced adult visits to the nest, but not differentially between males and females, which does not support our predictions. Our findings suggest (1) that sex differences in predator-induced behaviour could depend on the type of response (active vs. passive anti-predator strategies); (2) the potential existence of a minimum threshold in detectability between males and females for these behavioural changes to occur; and (3) the contrasting and opposite effects of several factors that might impede the selection of sex differences in these types of parental care behaviour. [ABSTRACT FROM AUTHOR]

We present a model for the evolution of host selection by avian brood parasites from the ecological context of siblicidal brood reduction tactics. Our analysis concentrates on the fitness costs and benefits that permit the evolution of brood parasitism as an adaptive strategy from a state of obligate parental care already featuring siblicide. Limited resources delivered by provisioning parents may incite siblicidal behaviour in offspring, directed towards nestmates regardless of kinship. The extent of siblicidal behaviour (in frequency of occurrence and number of nestmates killed) can extend to the eradication of all nestmates, as has been observed in some raptors and in seabirds. For parents of siblicidal offspring, laying each egg parasitically may maximize offspring survival by eliminating competition between related but siblicidal nest mates. To permit the evolution of conspecific (intraspecific) brood parasitism, costs of siblicide by the offspring of parasitic parents must exceed costs paid by the parasitic parents when losing related conspecifics (host offspring) in a host nest. To permit the evolution of obligate interspecific brood parasitism, costs to fitness from siblicidal offspring or nest reduction of related hosts must exceed costs of heterospecific parental care. Understanding the kin structure between parasites and hosts in conspecific parasitism, and measuring the costs paid by parasitic young due to mismatched incubation, provisioning, and social behaviours by heterospecific foster parents, should provide novel insights into the opportunities and constraints of the evolution of avian brood parasitism. [ABSTRACT FROM AUTHOR]

How hard do birds work during parental care, chick rearing, or provisioning of their nestlings? And if birds do work hard, can we detect a physiological signature of individual variation in workload ability (perhaps related to 'quality') or costs associated with high workload? Here, we provide a broad conceptual perspective on these questions. Life-history theory predicts (or requires) that (1) parental care is hard work, (2) individuals that invest more in parental care benefit in terms of rearing more, larger, fitter offspring, but that (3) increased investment in parental care comes at a cost: decreased future fecundity and/or survival. However, we start by highlighting studies that are inconsistent with this conventional view, e.g., (1) females often do not pay a survival cost of increased workload (though males do), (2) some (high quality?) individuals appear to maximise numerous life-history traits, and (3) workload during parental care often does not predict productivity. We suggest that an 'exercise physiology' perspective on parental care might be informative, but highlight the fact that existing models of exercise often involve conditions very different from that free-living animals experience while foraging (e.g., using forced exercise) and are often divorced from the critical relationship in free-living animals between exercise and acquisition of resources. We briefly review studies looking at physiological effects of workload during parental care in free-living birds, but again highlight our surprising lack of knowledge in this area especially where experimental manipulation of workload is coupled with comprehensive, physiological analysis. Finally, we make three recommendations for how can we advance the study of physiology of parental care in chick-rearing birds: (1) experimental manipulation of workload, (2) obtaining better measures of workload, for large numbers of known-individuals, and (3) better assessment of physiology of individual quality, and identification of specific metrics of workload-induced 'wear and tear'. [ABSTRACT FROM AUTHOR]

South temperate songbirds differ from north temperate species in life-history traits, having greater adult survival, smaller clutch size, longer developmental periods and extended parental care. Due to its broad distribution, the House Wren, Troglodytes aedon, is an excellent model to evaluate selective pressures that may influence the maintenance of present clutch size. Here we report data on life-history traits and parental care of socially monogamous House Wrens from a north temperate and a south temperate population. Southern House Wrens exhibited smaller clutch sizes and longer developmental periods than Northern House Wrens; however, we did not find significant differences in adult survival probability between populations, contrary to a critical prediction of the cost of reproduction hypothesis. Our data did not support the hypothesis that smaller clutches are the consequence of greater food limitation in the south. Southern wrens have greater adult body mass but smaller territories; southern nestlings reached a greater proportion of adult body mass 6-7 days before fledgling, and provisioning rates to the nest per nestling were greater in the south. We did not find support for the hypothesis that reduced clutch size is a consequence of limited parental activity at the nest as southern wrens did not reduce parental care during the incubation and nestling stage. Our data better supports the offspring quality hypothesis; southern wrens invest more per nestling than northern wrens as provisioning rates per nestling were significantly higher and developmental periods longer in the south. Published results from Tropical House Wrens suggest that neither food limitation nor nest predation can explain reduced clutches in Central America. We suggest that south temperate and tropical wrens may differ in parental investment strategies as tropical wrens seem to invest even less per nestling than north temperate wrens. [ABSTRACT FROM AUTHOR]

Understanding inter- and intraspecific variation in parental care has been an important focus in studies of avian behaviour and evolution. Unfortunately, typical methods for quantifying parental care, such as field observation and video recordings, can be extremely time-consuming. Here, we demonstrate that utilizing behavioural analysis software, such as EthoVision XT, can reduce time required for video data extraction by 37−69 %. This method is highly accurate; results and error rates did not differ from those of manual observation. We suggest this method could be beneficial and time-saving for studies analyzing large amounts of video recordings. [ABSTRACT FROM AUTHOR]

In precocial birds, adults select breeding areas using cues associated with habitat characteristics that are favorable for nesting success and chick survival, but there may be tradeoffs in habitat selection between these breeding stages. Here we describe habitat selection and intra-territory movements of 53 Piping Plover ( Charadrius melodus) broods (320 observations) during the 2007-2008 breeding seasons on mainland- and island-shoreline habitats at Lake Sakakawea, North Dakota, USA. We used remotely sensed habitat characteristics to separately examine habitat selection and movements at two spatiotemporal scales to account for potential confounding effects of nest-site selection on brood-rearing habitat used. The scales used were (1) the entire brood-rearing period within available brood-rearing areas and (2) 2-day observation intervals within age-specific discrete habitat selection choice sets. Analyses at both scales indicated that broods selected areas which were non-vegetated, moderately level, and nearer to the shoreline. Rate of brood movement increased with age up to 5 days, then stabilized; broods that hatched >50 m away from the shoreline moved toward the shoreline. Brood movements were greater when they were in vegetated areas, when the brood-rearing area was of greater topographic complexity, and when broods aged 6-25 days were further away from the shoreline. Using inferences from our results and those of previously published work, we postulate how a potential tradeoff in habitat selection between nesting and brood-rearing can contribute to an ecological trap in a novel habitat. This work, in the context of published works, suggests that plover breeding habitat is a complex of both nesting and brood-rearing habitats and provides a basis for making remotely sensed abundance estimates of suitable breeding habitat for Piping Plovers. [ABSTRACT FROM AUTHOR]

It has recently been demonstrated that male ornaments feedback on their physiological state and this is expected to be followed by behavioral alterations in paternal care. However, only a few studies have shown the effects of experimental manipulation of ornamentation on paternal care behavior. The present study investigated the effects of experimental manipulation of the size of a male ornament, the red throat patch, on the feeding rates of nestlings by male and female Barn Swallows ( Hirundo rustica gutturalis). First, we observed a dynamic change in male throat patch height during the breeding season, indicating that behavioral alterations in response to changes in throat patch height may be beneficial for male Swallows. Second, males with an experimentally reduced throat patch, but not their mates, fed their nestlings significantly more often compared with control individuals. In addition, we found a significant interaction between treatment and male body size: i.e., the effects of a reduced throat patch height varied depending on male body size. Among males with a reduced throat patch, male feeding rate increased with body size, but this was not the case in control males. This interaction is consistent with the idea that small males have low behavioral flexibility, and might contribute on positive correlation between throat ornamentation and male body size, given that behavioral flexibility is adaptive. The current finding indicates that males can increase paternal care in response to a seasonal decrease in ornamentation and this differential behavioral flexibility among males may facilitate the honesty of ornamentation. [ABSTRACT FROM AUTHOR]

Many species of tropical birds have prolonged incubation periods compared to other tropical species and to most species in temperate latitudes. One hypothesis for prolonged incubation is that these tropical species reduce nest attendance to minimize the risk of predation. The resulting decrease in average egg temperature would reduce embryo growth rate and lengthen the embryo development period. We sampled six species of Neotropical, lowland, inner forest antbirds (Thamnophilidae) and flycatchers (Tyrannidae) with average incubation periods between 17.9 and 23.3 days. Estimated total integrated 24-h nest attendance between clutch completion and hatching ranged between 14.2 and 19.5 days, representing 71-84 % of the incubation periods. Because total nest attendance in these species exceeded the incubation periods of most small passerine birds in temperate latitudes, and because average nest attendance per day did not differ substantially between these tropical species and temperate species, reduced nest attendance does not appear to cause their prolonged incubation periods. Instead, these extended egg periods likely reflect slower embryonic growth and development at a given egg temperature. Prolonged incubation can increase time-dependent mortality in the nest, which would require an increase in either post-fledging survival or adult reproductive success to favor a slow-growth evolutionary strategy. Mechanisms underlying the postulated trade-off between incubation period length and individual quality merit further investigation. [ABSTRACT FROM AUTHOR]

There is a growing body of evidence from across animal taxa that exposure to elevated levels of glucocorticoids during development can have profound long-term effects upon physiological and behavioral phenotypes. Several avian studies have revealed that the degree to which an individual's hypothalamo-pituitary-adrenal (HPA) axis responds to stressful stimuli as an adult may in effect have been 'programmed' or set as a result of that individual's corticosterone exposure in ovo or as a nestling. Developmental exposure to corticosterone may also have effects upon avian 'personalities' or coping styles, and evidence from mammalian studies suggests that these long-term effects are mediated epigenetically via altered expression of relevant DNA sequences. Although there does not appear to be a consistent across-species pattern, developmental exposure to elevated corticosterone levels may shape adult coping style with such exposure, resulting in adults that are more timid and with increased HPA axis responsiveness to stress than those individuals that were exposed to relatively little corticosterone as nestlings. Recent work in Florida Scrub-jays ( Aphelocoma coerulescens) has found that baseline corticosterone levels in nestlings at 11 days post-hatch explained 84% of the variation in 'personality' (bold vs. timid) when those individuals were tested at approximately 7 months of age. The overall 'personality' scores at 7-8 months of age were based upon tests that evaluated and combined the Jays' responses to three tests: two startle and one neophobia stimuli. Here, we present findings on some of the factors that contribute to corticosterone levels of nestling Florida Scrub-jays, both within and among broods. Our prior and continuing research, as this overview will present, suggests that maternal attentiveness at the nest and paternal provisioning are important factors that mediate nestling corticosterone levels. [ABSTRACT FROM AUTHOR]

Post-fledging care constitutes a large proportion of the total costs of parental care in many bird species. Despite being recognized as of critical importance to the survival of the offspring and their recruitment into the breeding population, post-fledging care, including the relative contribution by male and female parents, is under-studied. In this study, we quantified food provisioning (prey deliveries) by male and female Tengmalm's Owl ( Aegolius funereus) parents to their offspring both in the nestling and the post-fledging stages, in years of differing natural prey abundance. Parents and at least one offspring in 26 families were fitted with radio-transmitters. Male parents exhibited higher delivery rates than did females throughout the late nestling and post-fledging stages, but the intersexual difference was smaller in broods that were not deserted by the female at any stage. The female deserted her mate and offspring at some stage in 63% of the broods. Overall, deserted males delivered more prey to their offspring than did non-deserted males. Delivery rates were generally higher post-fledging. Prey delivery rates differed among years, and were highest in low vole years (probably because of smaller prey items), intermediate in peak vole years, and lowest in years of vole increase. Prey delivery rates increased with increasing brood size for both sexes, but the response was stronger in females. We suggest that female Tengmalm's Owls contribute less than males because they are in a position to decide on their level of provisioning effort first, and because of the potential for re-mating after deserting the first brood. [ABSTRACT FROM AUTHOR]

In cooperatively breeding birds, breeders can adjust their parental care investment without affecting nestling survival probability and save energy to invest in other activities, such as feeding, mating or territory defense. Furthermore, helpers at the nest can improve nestling nutrition and hence the reproductive performance of the breeding pair. We determined the influence of helpers on nestling feeding effort and reproductive success of breeders in the neotropical White-banded Tanager ( Neothraupis fasciata). We monitored nests during the breeding seasons of 2006 and 2007 in central Brazil. Males showed a compensatory reduction of their food delivery rate in the presence of helpers, whereas females exhibited the same parental effort regardless of having helpers. Total food delivery rate was higher for nests with helpers, but there was no effect of helpers on reproductive performance of breeders (clutch size, hatching rate, fledgling productivity and reproductive success). Our results indicate that cooperative breeding in the White-banded Tanager appears to be important for males to reduce their parental care effort and, hence, invest in their survival or future reproductive attempts. [ABSTRACT FROM AUTHOR]

The Predation Danger Hypothesis suggests that shorebirds adjust aspects of their annual schedules to limit the amount of time they are exposed to the danger posed by the presence of Peregrine Falcons ( Falco peregrinus) and other raptors. For example, Pacific Dunlin ( Calidris alpina pacifica) remain near their breeding grounds on the Yukon-Kuskokwim Delta, Alaska to molt, and migrate southward after peak Peregrine Falcon migration has passed. This extended residence in the north may enable them to increase the time they devote to reproductive activities and enhancing their reproductive output, either by increasing the length of bi-parental brood care or by producing more clutches. In this paper, I describe the breeding ecology of Pacific Dunlin and relate my results to their migration strategy. Pacific Dunlin females deserted their broods, on average, at 5 days of age, leaving the remainder of the 19-day brood care period to their mates. This resembles the parental care patterns of other Calidris species. However, Pacific Dunlin exhibited a high propensity for replacing first clutches that failed (75%), and 17% of individuals who successfully hatched their first nest deserted their broods and went on to produce a clutch with a new mate (i.e., double brood). These rates are high compared to other subspecies of Dunlin suggesting that Pacific Dunlin take advantage of their extended time on the breeding grounds to increase their reproductive output. [ABSTRACT FROM AUTHOR]

Labor division in parental care and reduction of inter-sex competition by division of the foraging niche have been suggested as part of the evolutionary basis for reversed sexual size dimorphism in boobies (Sulidae). To test the potential viability of both hypotheses for the maintenance of dimorphism, we studied parental care and foraging behavior of the Blue-footed Booby ( Sula nebouxii) in two colonies in the Gulf of California, Mexico. Proportion of time spent at the nest, feeding frequency, and time devoted to nest defense were used as indicators of parental care. Foraging ecology was evaluated through the number and duration of foraging trips, proportion of time dedicated to flight and to active feeding, rate and depth of diving, and diet. We found some inter-sex differences in foraging only under high demand conditions, such as food shortage or large broods. Inconsistent inter-sex differences seem to be part of a strategy to maximize chick rearing under a variable environmental regime. [ABSTRACT FROM AUTHOR]

The Spotted Barbtail ( Premnoplex brunnescens) inhabits the understory of humid montane forests in Central and South America. Apart from basic information on eggs and nest form, little has been published on its breeding ecology. Using temperature sensors in nest cups, I have collected data on the diurnal patterns of egg-coverage from three nests in eastern Ecuador and reveal a remarkable incubation rhythm. After providing near-constant coverage during the morning, adults leave the eggs unattended for most of the afternoon, returning to the nest only in the late afternoon. The mean duration (±standard deviation) of this period of absence, across the entire incubation period at three nests, was 6.4 ± 1.9 h. These results are discussed in relation to their physiological and ecological significance. [ABSTRACT FROM AUTHOR]

Parental care is assumed to be closely associated with individual differences in reproductive success. We investigated how feeding frequencies varied among parents and how this affected the subsequent reproductive success in insular populations of House Sparrows Passer domesticus in northern Norway. Female parents fed their offspring more than male parents did, and the feeding rates were positively related to the feeding rates of the partner. A positive relationship between feeding rates and bill depth was present in females. In males, the feeding rates were negatively related to total badge size and positively related to visible badge size, after the effect of other variables had been taken into account. A non-linear convex relationship between feeding frequency and hatch day was present in males, which could reflect either the seasonal change in weather conditions or the seasonal variation in food availability. For both sexes, feeding frequencies increased with increasing brood size, but at the same time the average feeding rate per nestling decreased with increased brood sizes. Finally, our results indicate that the amount of parental investment, measured as feeding rates during the nestling stage, may have a positive long-term influence both on the number of fledglings that recruit as well as the probability that fledglings survive until recruitment. [ABSTRACT FROM AUTHOR]

Brood-guarding (or the continual attendance at the nest by one parent) has been relatively little studied in altricial birds. Parental investment in brood-guarding is often highly variable within a species, and the study of such variability may contribute to the understanding of the functions and regulation of this behaviour and of the trade-offs involved in the choice between attending the nest and leaving to forage. In some colonial birds, it has been found that early nesting pairs attend their chick for longer than later nesting counterparts, giving rise to the synchronisation hypothesis that suggests that early pairs prolong brood-guarding in order to reduce the probability of nest predation by a dilution effect. In this paper, for the first time we test the prediction that burrow-nesting colonial birds subject to little predation pressure should not display a seasonal decline in brood-guarding duration. The growth assistance hypothesis suggests that brood-guarding may allow the provision of frequent small meals and the efficient use of energy by chicks with poor homeothermic capabilities, resulting in improved early chick-growth. Finally, the chick-protection hypothesis predicts that chicks in more exposed nests should be brood-guarded for longer. Data collected at two Cory’s Shearwater Calonectris diomedea colonies situated in contrasting environments supported the synchronisation hypothesis, as there was no seasonal trend in brood-guarding duration. Contrary to the growth assistance hypothesis, chicks brood-guarded for longer periods did not have an improved growth (in one colony there was even a negative effect of brood-guarding on early chick development). Finally, we found no difference in brood-guarding between nests with contrasting levels of exposure to potential predators and weather. Despite confirming the prediction of the synchronisation hypothesis, more research is needed to identify the main factors underlying the variability of brood-guarding observed in this and other studies. [ABSTRACT FROM AUTHOR]

Male investment of time and energy in caring for offspring varies substantially both between and within bird species. Explaining this variation is of long-standing interest to ornithologists. One factor that may affect male care is breeding site altitude, through its effects on climate. The harsher, less predictable abiotic conditions at higher altitudes are hypothesized to favour increased male investment of time and energy in offspring care. We tested this hypothesis by comparing male parental behaviour in Mountain Bluebirds ( Sialia currucoides) nesting at 1500 and 2500 m a.s.l. in the Bighorn Mountains of Wyoming, USA. We compared rates of prey delivery to nestlings at these two altitudes at two times: 1–2 days after hatching, when females spend much of their time brooding young, and 12–13 days later, when brooding has ended and nestling energy demands are peaking. High-altitude males fed nestlings 18 and 28% more often than low-altitude males early and later in the nestling stage, respectively, but only the difference in late-stage feeding rates were significant. Like males, females at the high site also fed nestlings significantly more often than females at the low site later in the nestling stage (45% difference in feeding rates). Consequently, the proportion of all feeding trips made by males at the high site (40%) did not differ significantly from that at the low site (44%). Parents at the high altitude may feed nestlings more often to compensate for their greater thermoregulatory costs. Parents may also be attempting to assist nestlings in storing fat and/or attaining a large size and effective homeothermy as quickly as possible to enhance nestling ability to survive bouts of severe weather which are common at high altitudes. [ABSTRACT FROM AUTHOR]

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Copyright of Journal of Ornithology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)