Reproductive Success Of Birds Research Articles

Nesting near road edges improves nest success and post-fledging survival of White-rumped Shamas (Copsychus malabaricus) in northeastern Thailand

ABSTRACT 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.

Reproductive success related to uropygial gland volume varies with abundance of conspecifics in barn swallows Hirundo rustica

Pathogens have negative effects on the fitness of their hosts, reducing survival and/or decreasing their reproductive success. To cope with pathogen challenge, animals have developed a variety of defensive traits to evade parasite infection and minimize their detrimental effects. Uropygial gland secretion has been proposed to have antimicrobial and antifungal properties, which may potentially influence bird fitness. However, whether uropygial gland secretion may affect the breeding success of birds remains unknown. Here, we explore whether the relationship between uropygial gland volume and reproductive success could be determined by the abundance of conspecific barn swallows (Hirundo rustica), a small colonial migratory hirundine. Because a larger number of swallows nesting within the same building may boost abundance and transmission of pathogens, we predicted that the anti-pathogen properties of uropygial gland secretion may enhance bird reproductive success in environments with high density of conspecifics. We showed that barn swallows with larger uropygial glands had higher breeding success (greater total number of fledglings reared) when living in environments with higher abundance of conspecifics. In contrast, barn swallows with larger uropygial glands had lower reproductive success when breeding in environments with lower abundance of conspecifics. Furthermore, we found that the same individuals did not modify uropygial glands in response to different pathogen pressure experienced across consecutive years. These outcomes suggest that benefits of uropygial secretion are host density dependent, thus consistent with this being a heritable trait that has evolved as a consequence of divergent selection imposed by pathogens. To face pathogen challenges, animals have evolved a broad range of barriers and defense mechanisms to avoid parasite infection and/or to minimize negative effects. Uropygial gland secretion has been proposed to have antimicrobial and antifungal properties, but also act as a defensive mechanism against malaria infection. However, whether uropygial gland secretions may affect the reproductive success of birds remains poorly studied. In this study, we explore, for the first time, whether the relationship between uropygial gland volume and reproductive success could be determined by the abundance of conspecifics. We found that barn swallows with larger uropygial glands had higher breeding success when living in environments with higher abundance of conspecifics. Because a larger number of swallows nesting within the same building may boost abundance and transmission of pathogens, this novel outcome is consistent with a heritable trait that has evolved as a consequence of divergent selection imposed by pathogens.

Effects of forest structure and harvest‐induced edges on predation risk

ABSTRACTManaged forest systems have implications for wildlife conservation because of their direct influence on condition and distribution of forest patches on the landscape. Spatial arrangement, structure, and composition of patches can influence reproductive outcomes for breeding birds by mediating nest site selection, survival, and predator–prey dynamics. Few studies have explored effects of local and adjacent forest‐stand structure and harvest‐induced edges on nest predation risk. Therefore, during summer 2014, we conducted artificial nest experiments within an intensively managed loblolly pine (Pinus taeda) landscape in Mississippi, USA. We used survival models to quantify effects of forest stand structure and proximity to harvest‐induced edges on apparent predation risk (APR). We conducted vegetation surveys and placed artificial nests (n = 146) at systematic distances from edges between 4 different pine stand types (Class 1: newly established stands; Class 2: 3–5 yr old; Class 3: 5–10 yr old; and Class 4: >10 yr old and postthinned). We sampled 4 stand pairs, each consisting of a Class 1 stand adjacent to a stand type of Class 1 (n = 4), 2 (n = 3), 3 (n = 4), or 4 (n = 4), and developed 15 a priori models relating APR to edge and vegetation characteristics. Apparent predation risk tended to be low and negatively related to edge where adjacent stands featured high proportion of shrub cover and vegetation density. We did not find strong evidence to support increased risk of nest predation near edges. These results were consistent with findings from studies in similar landscape contexts and suggest edges in forest‐dominated landscapes do not increase relative risk of nest predation. Rather, we found that APR was lowest in stands featuring dense shrub and vegetation cover that developed following clearcut harvest. Results of our study highlight some implications of forest harvest on reproductive success of birds, particularly those using early successional vegetation. © 2018 The Wildlife Society.

Experimental heatwaves negatively impact sperm quality in the zebra finch.

For sexually reproducing species, functionally competent sperm are critical to reproduction. While high atmospheric temperatures are known to influence the timing of breeding, incubation and reproductive success in birds, the effect of temperature on sperm quality remains largely unexplored. Here, we experimentally investigated the impact of ecologically relevant extreme temperatures on cloacal temperature and sperm morphology and motility in zebra finches Taeniopygia guttata We periodically sampled males exposed to 30°C or 40°C temperatures daily for 14 consecutive days. Following a 12-day (23°C) recovery period, birds were again exposed to heat, but under the alternate treatment (e.g. birds initially exposed to 40°C were exposed to 30°C). Elevated temperatures led to an increase in cloacal temperature and a reduction in the proportion of sperm with normal morphology; these effects were most notable under 40°C conditions, and were influenced by the duration of heat exposure and prior exposure to high temperature. Our findings highlight the potential role of temperature in determining male fertility in birds, and perhaps also in constraining the timing of avian breeding. Given the increased frequency of heatwaves in a warming world, our results suggest the need for further work on climatic influences on sperm quality and male fertility.

Attractiveness of male Zebra Finches is not affected by exposure to an environmental stressor, dietary mercury

ABSTRACT Choosing a high-quality mate contributes to increased reproductive success in birds. Females assess quality in males, in part, via condition-dependent signals such as songs and plumage. The production of these signals of quality can be disrupted by environmental stressors, including toxic pollutants such as mercury. Mercury affects song, plumage, bill color, and courtship behaviors in male birds, but the effect of these changes on female mate choice is unknown. By affecting the condition-dependent signals that females use to assess quality, mercury could alter males' attractiveness to females. We used mate choice of female Zebra Finches (Taeniopygia guttata) to determine if male attractiveness to females is affected by lifetime exposure to mercury. Males were either exposed to dietary mercury or left unexposed and then assessed by unexposed females in 3 types of mate preference tests: song-playback phonotaxis (preference for audio recordings of mercury-exposed or unexposed males' songs); 2-choice...

Predation risk of artificial ground nests in managed floodplain meadows

Nest predation highly determines the reproductive success in birds. In agricultural grasslands, vegetation characteristics and management practices influences the predation risk of ground breeders. Little is known so far on the predation pressure on non-passerine nests in tall swards. Investigations on the interaction of land use with nesting site conditions and the habitat selection of nest predators are crucial to develop effective conservation measures for grassland birds.In this study, we used artificial nests baited with quail and plasticine eggs to identify potential predators of ground nests in floodplain meadows and related predation risk to vegetation structure and grassland management.Mean daily predation rate was 0.01 (±0.012) after an exposure duration of 21 days. 70% of all observed nest predations were caused by mammals (Red Fox and mustelids) and 17.5% by avian predators (corvids). Nest sites close to the meadow edge and those providing low forb cover were faced with a higher daily predation risk. Predation risk also increased later in the season. Land use in the preceding year had a significant effect on predation risk, showing higher predation rates on unmanaged sites than on mown sites. Unused meadows probably attract mammalian predators, because they provide a high abundance of small rodents and a more favourable vegetation structure for foraging, increasing also the risk of incidental nest predations. Although mowing operation is a major threat to ground-nesting birds, our results suggest that an annual removal of vegetation may reduce predation risk in the subsequent year.

Species-specific nest predation depends on the total passerine nest density in open-nesting passerines

A large part of the variation in bird reproductive success is often explained by nest predation. Many studies report negative relationships between breeding density and reproductive success due to the predation effect. In this study, we tested the hypothesis that the total nest density should affect nest predation stronger than the nest density of a single species. We used a large sample (n = 320) of Booted Warbler Iduna caligata and Whinchat Saxicola rubetra nests obtained during a period of 6 years in abandoned fields. We used model selection to evaluate effects of density, nest age, season and year on daily nest survival rate. We used a single-species (the distance to the nearest conspecific nest and the number of conspecific nests around the focal nest) and total (the distance to the nearest nest of any passerine species and the total number of passerine nests around the focal nest) nest-density variables. Our results suggest that nest density affects nest survival negatively. Both Booted Warbler and Whinchat nests were more likely to be depredated when neighboring nests of any passerine species were closer. Daily nest survival rates were better predicted by the total nest density than single-species nest density. We suggest that generalist predators performing an area-restricted search may play an important role in nest predation in abandoned fields. The total nest density should be estimated when studying density-dependent nest predation as conclusions about nest predation based on single-species nest densities may be incorrect. The potential impact of density-dependent predation on real nests should be considered when designing artificial nest experiments.

Éxito de anidación de Turdus grayi (Passeriformes: Turdidae) en el Centro Ecológico Recreativo “El Zapotal”, Chiapas, México.

Nesting success has been a surrogate to assess environmental changes that affect the reproductive success of birds, and to analyze changes that influence natality. We analyzed the nesting success of Turdus grayi at "El Zapotal" Recreational Ecological Preserve, Central Chiapas. During the 2015 breeding season, we intensively searched for active nests and evaluated habitat characteristics. We located a total of 56 nests of which 27 (48.2 %) were successful and 29 (51.7 %) were unsuccessful. Most unsuccessful nests (19) were depredated, while 8 (27.6 %) were abandoned and 2 (6.9 %) parasitized. Nesting success was 46 %. Depredation was the main mechanism of nest failure, mostly during incubation. We identified operating variables at site and patch scales. Through analysis of binary logistic regression models for each scale, we predicted which variables increased the probability of nesting success. We also performed a multivariate logistic regression analysis to rule out possible interactions among variables. At nest scale we found that nest height, ranging 4.2 - 5.1 m had increased nesting success, while at patch scale, the probability of nest success was greater at sites with a tree density ≥ 12. Our results indicated that the probability of nesting success did not show a relationship between scales. We suggest a decoupling between scales and mechanism. Thus, habitat changes occurring at local scale did not seem to interfere with the patch scale. Also, our results showed that variation in characteristics at nest scale could also influence depredation, when depredation had been presented at random, since nests with medium and high probability of being successful, failed also for this reason. Thus, in order to understand the factors, mechanisms and life history characteristics influencing nesting success, we suggest that in addition to the environmental variables, future studies should also consider the bird nesting behaviour.

Do trace metals influence visual signals? Effects of trace metals on iridescent and melanic feather colouration in the feral pigeon

Trace metals are chemical pollutants of prime concern nowadays given their implication in several human diseases and their noxious effects on wildlife. Previous studies demonstrated their negative (e.g. lead, cadmium) or positive (e.g. zinc) effects on body condition, immunity and reproductive success in birds. Because of their effects on bird condition, trace metals are likely to influence the production of condition‐dependent plumage colours, that may be used in mate choice. In the feral pigeon Columba livia, we investigated iridescent colouration in response to lead and zinc experimental (i.e. metal supplementation in standardized conditions) and natural exposure (i.e. metal concentrations in feathers of wild urban pigeons), and melanic feather colouration in response to experimental lead and zinc exposure. Both studies (i.e. experimental and correlative) consistently showed that lead exposure decreased iridescent neck feather brightness independently of colour morph. Moreover, lead, when provided alone, decreased melanic feather reflectance in the middle wavelengths while zinc supplementation increased melanic feather reflectance in the violet‐wavelength. In conclusion, our study suggests that the colouration of iridescent and melanic feathers depends on the exposure to pollutants. Whether trace metal exposure affected the ability of birds to produce melanin pigments, to grow the microstructural feather elements required for maximum colour display, or to cope with bacteria that degrade feather microstuctures remains unclear. Future studies should investigate whether these metal‐induced modifications of plumage colouration affect behaviours involved in sexual selection.

Effects of crop type and harvest on nest survival and productivity of dickcissels in semi-natural grasslands

Recent focus on climate change and global energy production has increased interest in developing biofuels including perennial native grasses (e.g. switchgrass [Panicum virgatum]) as viable energy commodities while simultaneously maintaining ecosystem function and biodiversity. However, there is limited research examining the effects of biofuel-focused grasslands on grassland bird reproductive success and conservation. In 2011–2013 we studied the effects of vegetation composition and harvest regimens of switchgrass monocultures and native warm-season grass (NWSG) mixtures on nest success, nest density, and productivity for dickcissels (Spiza americana) in Clay Co. MS, USA. There was no effect of vegetation metrics, harvest frequency, or biofuel treatment on nest survival. However, both vegetation composition and harvest frequencies influenced nest density and productivity. Native warm season grasses contained 54–64 times more nests relative to switchgrass treatments, and nest density and productivity were 10% greater in single harvest plots. Our results suggest semi-natural grasslands can balance biofuel production, ecosystem functionality, and conservation so that biofuels offer an opportunity for wildlife conservation rather than a continued threat to grassland birds.

Mountain chickadees return to their post-natal dispersal settlements following long-term captivity

There is little work investigating the relationship between environmental changes and associated hippocampal effects on animal homing. We took advantage of previous studies in which wild, non-migratory mountain chickadees spent six months in captivity prior to being released. Over the following three years, 45.8% of the birds were resighted, and in all cases birds were identified less than 300 m from their initial capture locations at their respective elevation, despite previous studies documentingca30% captivity-related reduction of the hippocampus. Reproductive success of birds that spent six months in captivity did not differ from control birds that did not experience captivity. Our findings suggest that chickadees are highly site faithful and can return to their original capture location after spending time in captivity. Our results also have important implications for animal welfare practices as birds held in captivity bred successfully and may not need to be sacrificed following captivity.

Associations between birds and social wasps in the Pantanal wetlands

Nesting associations between birds and wasps may increase reproductive success of birds because the stings of these insects serve to protect the offspring against predators. The literature also reports the predation of wasps by birds and that these animals usually feed on the wasps during flight. Our aim was to report nesting associations between birds and social wasps and provide comments on wasp nest predation by birds in the Brazilian Pantanal wetlands. The study was conducted in the sub-region known as “Pantanal de Pocone”, state of Mato Grosso. We recorded seven associations involving four bird species: Paroaria capitata, Myiozetetes similis, M. cayannensis and Columbina talpacoti, and four wasp species: Polybia sericea, P. ruficeps xanthops, Chartergus globiventris and Parachartergus fraternus. One bird nest (14.28%), belonging to M. cayannensis, obtained reproductive success and was associated to P. sericea wasps. On the other hand, 42.85% of the nests were abandoned and 42.85% were preyed upon. A direct event of wasp nest predation was recorded, in which a group of White Woodpeckers attacked a nest of P. ruficeps xanthops. Other ten wasp nests were found with marks of predation made by birds. These were nests of Synoeca surinama (n = 2), P. chrysothorax (n = 2), P. ruficeps xanthops (n = 3), P. sericea (n = 2) and P. jurinei (n = 1), suggesting that social wasps may constitute an additional element in the diet of insectivorous birds. This study provides the basis for understanding the interactions between these two groups of animals.

Do natural areas in urban landscapes support successful reproduction by a group of conservation priority birds?

AbstractIf conservation priority birds are to persist in an increasingly anthropogenically altered world, suitable habitat must be created or preserved in potentially unsuitable landscapes. While natural areas in urban environments may provide habitat for declining groups of birds, little is known about effects of urbanization on the reproductive success of birds, such as grassland birds, that are typically thought to be associated with more rural landscapes. While typical conservation efforts have focused on conserving large patches of grassland in landscapes containing minimal amounts of woody vegetation and development, the assumption that habitat located in developed landscapes is of poor quality has not been tested and may wrongly devalue grasslands located in an urban matrix. To examine the influence of development on habitat quality for grassland birds, we studied grassland bird nest predation and brood parasitism in patches of varying size along an urbanization gradient in northeastern Illinois. Because nest predation is the primary cause of reproductive failure and a potentially limiting factor for grassland bird populations, we used miniature video cameras to identify predators at a subset of nests. From 2012 to 2013, we monitored 432 nests of 16 grassland bird species. Nest predation rates decreased with urbanization in the landscape as did probability of brood parasitism. We filmed 44 nests and documented 19 predation events. We found that coyotes Canis latrans, white‐tailed deer Odocoileus virginianus and thirteen‐lined ground squirrels Ictidomys tridecemlineatus were important nest predators in our study system. Contrary to prior assumptions, our results suggest that grasslands located in urban landscapes may provide habitat of equal or greater quality than many rural grasslands.

Avian feathers as a non-destructive bio-monitoring tool of trace metals signatures: A case study from severely contaminated areas

The concentrations of trace metals were assessed using feathers of cattle egrets (Bubulcus ibis), collected within two industrial areas of Pakistan, Lahore and Sialkot. We found, in order of descending concentration: Zinc (Zn), Iron (Fe), Nickel (Ni), Copper (Cu), Cadmium (Cd), and Manganese (Mn), Chromium (Cr), Arsenic (As), and Lithium (Li), without any significant difference (except Fe, Zn, and Ni) between the two areas. The concentrations of trace metals, we recorded were among the highest ever reported in the feathers of avian species worldwide. The concentrations of Cr, Pb, Cd were above the threshold that affects bird reproductive success. The high contamination by heavy metals in the two areas is due to anthropogenic activities as well to natural ones (for As and Fe). The bioaccumulation ratios in eggs and feathers of the cattle egret, their prey, and the sediments from their foraging habitats, confirmed that avian feathers are a convenient and non-destructive sampling tool for the metal contamination. The results of this study will contribute to the environmental management of the Lahore and Sialkot industrial areas.

Sperm depletion does not account for undeveloped eggs in Blue Tits Cyanistes caeruleus

Hatching failure negatively impacts reproductive success in birds. One reason why eggs fail to hatch is that they are not fertilized, which may be because they receive insufficient sperm. In most passerines, copulation declines in frequency or ceases altogether after the laying of the first egg, so eggs laid late in the laying sequence may be more likely to remain unfertilized. We tested this prediction in the Blue Tit Cyanistes caeruleus, a species in which late‐laid eggs are particularly likely to be sperm‐limited because it lays the largest clutch of any passerine. We assessed whether: (1) eggs laid later in the laying sequence are more likely to fail to develop, (2) larger clutches are more likely to contain undeveloped eggs, (3) the number of sperm present on the perivitelline layers of each egg decreases across the laying sequence and (4) the number of sperm present on the perivitelline layers of freshly laid eggs sampled from active clutches predicts the proportion of eggs that develop in the remainder of the clutch. The occurrence of undeveloped eggs was not related to their position in the laying sequence, nor was it related to clutch size. Within a clutch, sperm number did not differ between an egg laid early and an egg laid towards the end of the laying sequence. Moreover, there was no indication that the proportion of undeveloped eggs in a clutch correlated with the number of sperm in a subset of eggs from that clutch, or that females laying larger clutches had stored more sperm. In summary, we found no evidence that Blue Tit eggs fail to hatch because they receive insufficient sperm.

Effect of intermittent incubation and clutch covering on the probability of bacterial trans‐shell infection

Microbial infection is considered a critical cause of hatching failure in birds. Although several behavioural mechanisms are believed to improve reproductive success in birds, their direct effect on the risk of bacterial trans‐shell infection (BTSI) remains to be tested. Here, we focus on the protective roles of intermittent incubation and covering of the clutch with nest lining during the laying period, when eggs are highly susceptible to BTSI. To our knowledge, this study is the first to use culture‐independent PCR‐based methods to measure quantitative and qualitative indices of BTSI. In our experiment, we exposed Mallard Anas platyrhynchos eggs that were either intermittently incubated (I‐INCUB) or un‐incubated (I‐UNINCUB), and covered (COV) or uncovered (UNCOV) with nest lining. Hatchability of I‐INCUB eggs was twice that for I‐UNINCUB eggs. The presence and degree of BTSI had no effect on hatching success of experimental eggs. The residual weights of ducklings hatched from infected and I‐INCUB eggs were lower than those from uninfected and I‐UNINCUB eggs. In addition, ducklings originating from COV eggs were heavier than those hatched from UNCOV eggs. Intermittent incubation and clutch covering had no effect on the probability or degree of BTSI. Although the effect of BTSI is considered less detrimental in temperate birds, we show that the presence of BTSI inside the egg may significantly affect hatchling phenotype. This represents a novel insight into the role of BTSI in the reproductive success of birds and implies that the use of molecular PCR‐based methods is required in future studies for a better understanding of such causality.

Endocrine status of a migratory bird potentially exposed to the Deepwater Horizon oil spill: A case study of northern gannets breeding on Bonaventure Island, Eastern Canada

The Deepwater Horizon oil spill caused the death of a large number of seabirds in the Gulf of Mexico in 2010. However, the long term consequences of oil exposure on migratory birds overwintering in this area have received limited attention. The present study aimed to investigate the impact of oil contamination (e.g., polycyclic aromatic hydrocarbons (PAHs)) on the circulating status of prolactin and corticosterone, two hormones that influence reproductive success in birds, in Northern gannets (Morus bassanus) breeding on Bonaventure Island, Eastern Canada. Using light-based geolocators, it was found that 23.5% of Northern gannets from Bonaventure Island overwintered in the Gulf of Mexico in 2010–2011; the remainder of this population overwintered along the Atlantic Coast of the United States. PAH concentrations (eight compounds) in gannet blood cells were all found to be under the method limits of quantification, which could be the result of the ability of seabirds to metabolize these compounds and the time elapsed between oil exposure and blood sampling. Corticosterone and prolactin levels as well as body mass did not differ between the two major birds' wintering sites. Moreover, levels of both these hormones did not vary from early to late incubation period. Present results suggest that if Bonaventure Island-breeding Northern gannets had been exposed to oil in the Gulf of Mexico in the aftermath of this historical spill, this exposure could not be associated with changes in hormonal status and body mass in breeding individuals.

Polybrominated diphenyl ethers and multiple stressors influence the reproduction of free-ranging tree swallows (Tachycineta bicolor) nesting at wastewater treatment plants

Reproductive success of birds is influenced by maternal factors, ambient temperatures, predation, food supply, and/or exposure to environmental contaminants e.g., flame retardants (FRs). Reproduction of tree swallows (Tachycineta bicolor) was compared among waste water treatment plants (WWTPs) and a reference reservoir in Ontario, Canada (2007–2010), to determine the importance of exposure to polybrominated diphenyl ether (PBDEs) FRs within a complex contaminant cocktail, relative to natural and biological factors known to influence avian reproduction. The birds primarily consumed insects emerging from the reference reservoir and WWTP outflows, where effluent mixed with receiving waters. FR egg concentrations were dominated by 5 PBDE congeners (∑5PBDEs): 2,2′.4,4′,5-pentabromodiphenyl ether (BDE-99), 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47), 2,2′4,4′,6-pentabromodiphenyl ether (BDE-100), 2,2′,4,4′,5,5′-hexabromodiphenyl ether (BDE-153), and 2,2′,4,4′,5,6′-hexabromodiphenyl ether (BDE-154), with much lower concentrations of decabromodiphenylether (BDE-209), hexabromocyclododecane (HBCDD), and novel FRs. Although higher than ∑5PBDEs, polychlorinated biphenyls (PCBs) egg concentrations were unlikely to affect the swallows' reproduction. Clutch size and timing, fledging, breeding success, and predation, varied significantly among sites, generally being poorer at WWTP1 and better at WWTP2. The early reproductive stages were sensitive to some FRs at measured concentrations. The ∑5PBDEs, maternal age, and minimum ambient temperatures predicted onset of egg laying in the most parsimonious statistical model, and there were positive relationships between egg size and HBCDD or BDE-209 concentrations. However, there were no significant correlations with any reproductive measures, individual BDE congeners or low concentrations of novel FRs, in this first such report for novel FRs and wild birds. Tree swallows are passerines, and passerines may differ from birds of prey in their reproductive sensitivity to PBDE exposure: lay date, minimum temperatures, and predation, but not PBDE exposure, predicted reproductive productivity. Overall, there was some influence of the PBDEs available in these WWTP outflows on early reproductive parameters, but not reproductive output, of these passerines.

Body condition dynamics and the cost‐of‐delay hypothesis in a temperate‐breeding duck

Pre‐breeding body condition is an important determinant of reproductive success in birds, largely through its influence on timing of breeding. Declines in clutch size and recruitment probability within breeding seasons indicate a tradeoff may exist between the number of young (clutch size) and quality of young (recruitment probability). We explored local drivers of pre‐breeding body condition and tested predictions of the cost‐of‐delay hypothesis in female lesser scaup Aythya affinis. Yearling females arrived on the study site in lower body condition than older females, but both age classes had similar rates of body condition gain on the breeding grounds prior to nesting. Rates of body condition gain were positively influenced by water temperature, a proxy for wetland phenology. The effect of water level was asymptotic and interacted with water temperature, with greater rates of gain in body condition occurring in years with low water levels. Our results supported the predicted response of clutch size to the rate of pre‐breeding body condition gain. After accounting for lay date, clutch size was positively related to the rate of body condition gain (= 0.08 ± 0.039). We did not find support for a predicted interaction between rate of body condition gain and intra‐seasonal decline in clutch size (= 0.01 ± 0.01). Our results indicate that local conditions during pre‐breeding influence body condition dynamics in female lesser scaup, which subsequently affects clutch size.

Modelling urban populations of the Australian White Ibis (Threskiornis molucca) to inform management

AbstractSince the 1970s, populations of the Australian White Ibis (Threskiornis molucca) have dramatically increased in many Australian urban centres. Managers of ibis are currently focusing on limiting this bird's reproductive success in order to reduce population sizes or at least halt further increases in urban areas. Here we use data on nesting success and survival for three populations of ibis around greater Sydney to develop an age‐structured population model. The estimated growth rate for all populations combined was about 1.5 % per year and for individual sites were more variable at −1, −7, and 9 %. For all populations, growth rates were most sensitive (based on elasticity analyses) to the survival of adults and least sensitive to fecundity, especially of 3 year olds. Further exploration of the importance of fecundity rates, which are relatively poorly known for these populations, suggests that rates of <0.4 fledglings per nest per year is very likely to lead to a population decline (λ less than lower bound of 95 % CI). Conversely, positive population growth is nearly assured (λ greater than upper bound of 95 % CI) for fecundities of >0.7 fledgling per nest per year. The results suggest that ibis from other locations (probably their traditional breeding areas in inland Australia) have immigrated into urban environments as estimated growth rates cannot account for current population sizes. Management strategies must take these findings into account and also consider that ibis are declining in their traditional habitats to avoid exacerbating their decline at a regional scale.