Nest Failure Research Articles

Cages Mitigate Predation on Eggs of Threatened Shorebirds: A Manipulative-Control Study

Beach-nesting birds (plovers; Aves; Charadridae) are impacted by many natural and human-induced threats (e.g., people trampling, dogs, and natural predators). In this regard, the use of anti-predator cages on their nests is effective in order to mitigate some of these pressures (i.e., predation). To evaluate the efficacy of anti-predator cages and the causes of nest failure in a breeding site of two species (Charadrius alexandrinus and C. dubius), we carried out a control-experimental design, comparing false nests (n = 69) in cages (experiment; n = 30) with false nests without cages (control; n = 39). We carried out the study in three seasonal periods (May, June, and July), controlling predations after three periods (three, six, and nine days) since positioning, recording the frequency of eggs still present and evidencing any predation event. The percentage of residual eggs was significantly higher in experimental nests when compared to control nests in all recording periods. Considering 59 predation events on false nests, the most important predators were: in experimental nests (n = 21) the fox, Vulpes vulpes (47.6%), and in control nests (n = 38), the hooded crow, Corvus cornix (50%). Our data suggest that the use of anti-predator cages significantly limits predation on eggs and therefore is likely to increase the hatching success in these ground-nesting birds independently in the seasonal period. However, also in the presence of a cage, the fox is a relevant egg predator.

Nest survival of the Snowy Plover Charadrius nivosus at Marismas Nacionales, Nayarit

Breeding habitat loss and nest predation are considered the main causes of Snowy Plover (Charadrius nivosus) populations decline worldwide. We evaluated the effects of season, nest age, distance to nearest vegetation patch, distance to nearest body of water, habitat type, and nesting substrate on the daily survival rate of Snowy Plover nests. During 2014-2015, we located 84 nests in Las Garzas-Chahuin-Chihua lagoon in Marismas Nacionales, Nayarit, Mexico. We used MARK software to estimate daily nest survival rate, which was 0.969 (95% CI = 0.95 - 0.97) for both breeding seasons combined, with a 42% finite nesting success. A total of 44 nests (52%) were successful, while 40 (48%) failed. The main causes of nest failure were predation (n = 30; 75% of failed nests) and flooding (n = 9; 22.5% of failed nests); one nest was lost due to unknown causes (2.5%). Daily survival rate increased with nest age and distance from the nearest vegetation patch. By contrast, daily survival rate decreased with the progression of the breeding season; a higher probability of nest success was evident when established early in the breeding season. Our results show the importance of different positive and negative factors influencing nest survival that might be considered as part of conservation strategies.

Nest density, egg conspicuity, vegetation structure and seasonality affect artificial nest predation in the Brazilian Cerrado

AbstractNest predators use visual, acoustic and chemical cues to locate nests. In the Neotropics, predation is high being the main cause of nest failure. Despite that, it is still not completely clear what kind of information predators are using to find nests or whether predators respond differently according to habitat characteristics. Here, we executed an experimental manipulation to investigate how different ecological factors influence nest predation probability. We hypothesised that egg conspicuousness, nest clustering and a more open vegetation structure would increase nest predation probability, and that nest predation would be higher during the breeding season of most avian species in the region. We used artificial nests baited with plasticine and quail eggs (Coturnix coturnix), manipulated egg coloration and nest density. Artificial nests were distributed over forest and savanna-like vegetations. Overall predation rate was 40.9%. We found that nests baited with conspicuous eggs, located in open habitats, at higher densities and during the dry period were more predated. Results suggest that main predators must be visually orientated, and that egg crypsis is an important trait for open-nest species in the area. Moreover, a higher nest density may affect predator behaviour, favouring an increase in nest searching, which may be facilitated in open habitats.

Impact of Water Fluctuation from a Dam on the Mekong River on the Hatching Success of Two Sandbar-Nesting Birds: A Case Study from Bueng Kan Province, Thailand

Dam construction for the provision of hydropower and a stable water supply poses a major threat to freshwater biodiversity. Water fluctuation due to dam management has adverse effects on local people and biodiversity in downstream areas, including sandbar-nesting birds. The aim of this research was to determine the effect of water levels controlled by upstream dams on the breeding success of two sandbar-nesting birds, the little ringed plover, Charadrius dubius, and little pratincole, Glareola lacteal, along the Mekong River in Bueng Kan Province, Thailand. During January–May 2018, we found 160 active nests of only two species, the little ringed plover (n = 26 nests, 288 exposure days) and the little pratincole (n = 134 nests, 890 exposure days). Their nest success rates were 19.49 ± 7.52% and 5.54 ± 1.61%, respectively. Predation was a major cause of nest failure for both species (n = 82), followed by flooding (n = 44). We found a significantly increased probability of nest flooding when the water level was higher than when the nest was initiated for those located closer to the water, particularly during March and April, when water levels fluctuated. Our results indicate that dams threaten sandbar-nesting species.

Nesting biology of the Hudson´s Canastero (Asthenes hudsoni) and the Bearded Tachuri (Polystictus pectoralis), two threatened and poorly known birds of the Pampas grasslands

ABSTRACT The accelerated rate of grasslands transformation has led to noticeable population declines of many grassland bird species. Although several species of the Pampas grasslands are of conservation concern, the information on their nesting biology is generally sparse. During three consecutive breeding seasons (2018–2019 to 2020–2021), we studied nesting attempts of two of the most threatened grassland bird species in central-eastern Argentina: the Hudson’s Canastero (Asthenes hudsoni) and the Bearded Tachuri (Polystictus pectoralis). We found 16 nests of Hudson’s Canastero and seven nests of Bearded Tachuri in natural grasslands. In both species, the modal clutch size was three eggs, and predation was the main cause of nest failure. Incubation and nestling periods lasted 15 and 11.5 days for the Hudson’s Canastero and 14.3 and 12 days for the Bearded tachuri. Daily Survival Rates were 0.90 and 0.97, resulting in a cumulative survival of 4% for the Hudson’s Canastero and 39% for the Bearded Tachuri. We found that the breeding biology of the two threatened grassland bird species is strongly tied to tall native grasslands and suggest that both species could be sensitive to changes in breeding habitat, particularly in the grassland vegetation structure.

Effects of nest site selection and nest concealment on nest survival of Gosling's Bunting (Emberiza goslingi)

Selecting nest sites that provide access to resources and reduce predation risk is crucial to maximizing fitness in breeding birds. Therefore, understanding what habitat features influence nest site selection and nest success is a key component of avian conservation because it allows for identification and protection of habitat that will promote population growth. We examined drivers of nest success in Gosling's Bunting (Emberiza goslingi) by evaluating variables that influence nest site choice and nest survival at 23 nests and an equal number of random, paired, non-nesting locations in a tropical savannah landscape in north-central Nigeria. Gosling's Buntings exhibited a nonrandom nest-placement pattern. Nests were either on or in proximity to large rock surfaces with nesting probability increasing when the immediate nesting area (100 m radius around the nest) consisted of 30–60% bare rock. Compared to random non-nesting sites, buntings selected areas that were low in litter cover and/or had short grass height. Daily nest survival probability was high (0.96) and was positively associated with the proportion of bare rock around the nest but negatively with the amount of litter cover. Although hatching success was 56.9%, only 30% of all nesting attempts successfully fledged a chick suggesting that nest failure occurred mostly at advanced stages of nesting (nestling phase) when renesting is less likely. Nest survival was higher at low concealment, but only significantly higher than nest failure within a restricted concealment range of 45–54%. Our findings show that microhabitat features could benefit reproduction and daily nest survival. Furthermore, by linking nest-site attributes with fitness indices, we highlight the potential importance of fitness measures as a key component of habitat quality assessment for these buntings in tropical savannahs.

Breeding Biology of the Endangered Burrow-Nesting Lesser Crescent-Chested Puffbird Malacoptila minor

For many birds breeding success may be related to the availability of nesting sites, particularly in ecologically specialized cavity-nesting birds. For burrow-nesting species, the selection of an appropriate substrate may be fundamental to a successful breeding attempt. The Lesser Crescent-chested Puffbird Malacoptila minor is a bucconid with a restricted distribution, which is found in the states of Maranhão and Piauí, in northeastern Brazil. It is the only bucconid listed as threatened with extinction, and little is known about its natural history. A total of 49 nests were found over three breeding seasons (2017–2020). Nests consist of burrows dug in the ground that are used only once for breeding. Incubation lasted 21.2 ± 1.3 days and the nestlings fledged after 19.5 ± 2.9 days. The nests contained two or three eggs. The mean hatching rate was 0.46 ± 0.47 eggs per nest and the fecundity rate was 1.0 fledgling per female. The production was 0.53 fledglings per nest, apparent reproductive success was 22.4% (N = 49), and was 15.7% (N = 49) when based on Mayfield's protocol. The probability of breeding success per period was greater during the incubation phase than during the nestling phase. Predation was identified as the principal cause of nest failure (77.5%), mainly during the incubation phase. Three predators were identified: the Crab-eating Fox Cerdocyon thous, the fire ant Solenopsis saevissima, and a lizard, the Common Tegu Salvator merianae. Breeding season starts with the onset of rainy season and nest flooding did not appear to be a concern, which contrasts with the available data on other bucconids. The results of the present study are the first data on the breeding biology of the Lesser Crescent-chested Puffbird, and represent an important advance in the understanding of breeding patterns in the Bucconidae.

Temporal factors and distance to human settlement affect nest survival of the endangered Yellow-headed Parrot in Belize, Central America

AbstractThe endangered Yellow-headed Parrot (Amazona oratrix) has experienced a considerable reduction in abundance and distribution. Identifying natural and anthropogenic causes of nest failure is a critical step towards developing conservation actions that increase nest survival. In this study, we examined daily nest survival in relation to temporal, habitat, and anthropogenic factors, as well as nest site properties. We monitored nests (n = 124) across 6 study sites in Belize during 2017 and 2018 and independently modeled the effects of predation, abandonment and poaching on daily nest survival rates. Overall, the estimated cumulative nest survival probability was 0.18 (95% CI: 0.12–0.25). Predation was the main cause of nest failure, followed by abandonment, and poaching. Our results showed that nest predation and abandonment usually occurred early in the nesting cycle. Day within the nesting season negatively influenced daily survival for abandoned nests and had a quadratic effect on survival for poached nests. Poaching events occurred at a specific date range later in the season, with nests farther from the nearest human settlement having higher daily survival. Findings from this study highlight the additive mortality effect that nest poaching is having on Yellow-headed Parrot populations in Belize and show that managers can anticipate the timing and location of nests most vulnerable to poaching.

Stronger negative species interactions in the tropics supported by a global analysis of nest predation in songbirds

AbstractAimSpecies interactions are assumed to be stronger closer to the equator. However, numerous studies provided conflicting results and considerable controversy exists concerning the latitudinal patterns in the intensity of biotic interactions. Thus, the question of whether biotic interactions are stronger near the equator remains open. Here, we provide a global evaluation of latitudinal trends in nest predation in songbirds and their explanations.LocationWorldwide.TaxonSongbirds (Aves: Passeriformes).MethodsWe collected published data on nest predation in 1297 populations of 659 species across the globe (124,958 nests). We quantified latitudinal trends in the intensity of nest depredation (daily predation rate, DPR) and in potential demographic impacts of nest depredation (the proportion of nests destroyed by predators). We also quantified the latitudinal trend in the proportion of failed nests destroyed by predators and assessed how nest depredation and latitudinal trends differed across nest types. We aimed at explaining spatial variation in nest predation by productivity and species richness of potential nest predators.ResultsAll measures of nest predation increased towards the equator and the increase was stronger in the northern hemisphere. Nest predation also increased with time, and it was higher in open nests than in cavities. Nest predation increased with productivity (indexed by NDVI), independently of latitude. It also increased with species richness of potential nest predators, but this effect was confounded with latitude.Main conclusionsTropical songbirds faced both higher intensity of nest predation (higher DPR) and more detrimental demographic outcomes of nest depredation (higher proportion of nests lost to predators). Moreover, the proportion of nest failure caused by predators also increased towards the equator. Our results support the view that birds are subject to strong biotic interactions close to the equator. Nest predation increased with productivity and tended to increase with species richness of potential nest predators.

Nest predation, brood parasitism and the reproductive success of the masked laughingthrush Garrulax perspicillatus in the rural habitat of central China

Knowledge of nest site selection and reproductive ecology is fundamental to understanding the evolution of life history traits and developing species conservation strategies. However, life history traits of species in the genus Garrulax are poorly known. Particularly, research on the breeding biology of Garrulax perspicillatus in their natural habitat and comparison between populations in different environments (rural vs urban) are lacking. We presented data of nest site selection and breeding ecology of Masked Laughingthrush in central China during 2021, and made a detailed investigation on nest predation and interspecific brood parasitism. The breeding season began from March and ended in August. Most nests were built on Sulphur Bamboo ( Phyllostachys sulphurea). First egg laying occurred between late March and late July. Incubation period lasted 13.9 days (±0.3 SE; 13–15) and nestling period of 13.1 days (±0.2 SE; 12–15). Average clutch size was 3.8 eggs (±0.1 SE; 3–7), and brood size at fledging was 2.7 young (±0.2 SE; 1–4). Overall, 36.2% of nesting attempts successfully fledged at least one young. Nest predation (0% in March, 38.2% in April, 30.0% in May, 20.0% in June and 27.3% in July) and interspecific brood parasitism (13.3% in May, 40.0% in June and 36.4% in July) were two main reasons for nest failure. This is the first study that provided detailed information of breeding ecology of Masked Laughingthrush in rural habitat, and we discussed the difference of life history traits between urban and rural habitats.

Age-specific effects on reproductive performance of grassland songbirds nesting in agricultural habitats

Clutch size and number of young fledged has been shown to increase with female age until approximately mid-life, when reproductive performance declines. We used a long-term dataset (2002–019) to investigate age-specific effects on reproductive parameters of known-age female Savannah Sparrows (<em>Passerculus sandwichensis</em>, n = 60), and Bobolinks, (<em>Dolichonyx oryzivorus</em>, n = 75) breeding in managed hayfields and pastures in Shelburne and Hinesburg, Vermont, USA. Female Savannah Sparrows (age 1 to 6 years) showed evidence of reproductive senescence with the number of young fledged peaking at 2 years of age and declining in older age classes. Additionally, daily nest survival was strongly and negatively affected by female age. The effect of age on Bobolink reproductive performance was weak. We found an increase in the number of eggs laid from 1 to 2 years of age, no age effect on number of nest attempts or number of young fledged, and a weak, negative effect of age on daily nest survival. We found no support for an effect of grassland management treatment on daily nest survival, which may have been a result of unequal distribution of nesting attempts across treatment types. However, species-specific responses to hay harvest may have affected the relationship between age and reproductive performance. Savannah Sparrows renest rapidly and frequently after nest loss due to haying, which may constrain long-term investment in reproduction. In this highly managed system, older females may allocate less energy toward reproduction than younger females, potentially shifting those resources to behaviors that support annual survival. By contrast, Bobolinks may not invest as heavily in reproduction, generally renesting only once after nest failure and have a truncated breeding season because of their long fall migration to South America. Consequently, their reproductive success may not vary as strongly with age.

Nest remains are insufficient to identify predators of waterfowl nests

Context Nest predation is a leading cause of nest failure for most ground-nesting birds. Methods that allow for accurate classification of fate and identification of predators are important for understanding productivity and conservation strategies. Past studies have used a visual inspection of nest remains to determine nest fate and predict predator identity. Most formal assessments of these methods have addressed small-bodied birds nesting in trees or shrubs, and have revealed that use of evidence at nests can be relatively accurate for determining nest fate but may lead to incorrect conclusions regarding predator identity. However, few have tested the latter hypothesis for larger ground-nesting birds with precocial young. Aim We aimed to evaluate a classification system developed for determining nest fate and identifying predators of waterfowl nests, at both the scale of individual nests and across the study area. Methods From 2016 to 2020, we located 989 blue-winged teal (Spatula discors), mallard (Anas platyrhynchos) and gadwall (Mareca strepera) nests in central North Dakota. We placed cameras at a subset of 249 nests and recorded evidence of nest remains at depredated nests. Key results The most common predators were American badgers (Taxidea taxus), followed by striped skunks (Mephitis mephitis), raccoons (Procyon lotor) and red foxes (Vulpes vulpes). Using evidence of nest remains, we determined nest fates with high accuracy (98.0%). However, evidence of nest remains was only sufficient for identifying predators at 50% of nests, and the classification system was correct only 69.7% of the time. The predicted proportion of predators across the study area differed between the classification system and our video evidence as well. Conclusions The accuracy of predator identifications based upon the classification system that we evaluated was not supported at any scale. Implications Our results suggest that evidence of nest remains can be used to determine nest fate for large-bodied precocial, ground-nesting birds, but accurate identification of nest predators will require alternative methods such as nest cameras.

Helpers during replacement clutches buffer the impacts of late breeding on a cooperative bird

Renesting is an important strategy employed by many bird species to compensate for nest failure. However, although replacement clutches may increase an individual's annual reproductive success, they impose substantial energetic and fitness costs. In some cooperatively breeding species, helpers lighten breeders' workloads thereby facilitating a second clutch within a season or increasing their survival prospects. Alternatively, renesting may increase the chances of having help in replacement clutches as some individuals that have lost their own clutch could redirect their parental effort to another nest. Here we used a 20-year dataset of a facultative cooperative breeder, the Iberian magpie, Cyanopica cooki , to investigate how helping and renesting behaviours combine to affect reproductive output. After controlling for clutch size and laying date, we show that helpers had a positive effect on the reproductive success of pairs, particularly in replacement clutches. Indeed, our study revealed that replacement clutches were much more common than previously thought (observed in three-quarters of the females that lost the first clutch), and that the probability of receiving help was higher in replacement clutches. As helpers increased in number over the breeding season, they could contribute to buffering the negative effects of breeding late, when environmental conditions can be more adverse, and the probability of successful independent reproduction is lower. This study indicates that species with cooperative breeding and a short lifespan can prioritize current over future reproduction by renesting at the end of the breeding season, when the benefits of having help outweigh the costs associated with deteriorating environmental conditions. We propose that renesting can be a context-dependent strategy (mediated by social and environmental factors) that may increase reproductive success in avian cooperative breeding systems. • Renesting is an important context-dependent strategy in Iberian magpies. • Probability of receiving help is higher in replacement than in first clutches. • Helpers increase reproductive success, but more so in replacement clutches. • Helpers thus contribute to buffer the negative effects of late breeding.

Reproductive Ecology and Nest Success of Reddish Egrets (Egretta rufescens) on a Natural Marsh Island in Southwestern Louisiana, USA

The Reddish Egret (Egretta rufescens) is considered a species of conservation concern throughout its range, primarily due to high rates of coastal land loss at key nesting locations. Nest and brood survival, causes and timing of nest failures, as well as nest site characteristics and site selection were studied for three breeding seasons (2016-2018) on a natural marsh island in southwestern Louisiana, USA. Of 110 nesting attempts, 58.2% hatched at least one egg. During incubation, overall daily survival rate was 0.979 (± 0.003 SE), corresponding to 56.4% success from egg laying to hatching. For broods, daily survival rate was 0.993 (± 0.002 SE), or 72.9% success from hatching to fledging. Overwash was identified as the primary cause of known nest and brood loss, accounting for 48.9% and 27.8% of all nest and brood failures, respectively. Overall productivity for breeding pairs within the study area was 1.06 chicks/pair for all years. Data suggests that overwash from extreme high tides and wind can significantly contribute to lower reproductive success of breeding pairs but the lack of mammalian predators on the island may contribute to increased nest success, especially in years that do not experience high water levels.

Video Monitoring of Waterbird Colonies Reveals Novel Predator

Beach nesting waterbirds are among the most vulnerable groups of birds that are threatened by climate change, habitat loss, predation, and human disturbance. To improve conservation management strategies, causes of nest failure for ground-nesting waterbirds and effectiveness of mammalian predator control were investigated. Changes in breeding population size and hatching success of Royal (Thalasseus maximus) and Sandwich (T. sandvicensis) terns were evaluated based on pre-mammalian removal (2012-2014) vs. post-mammalian removal (2015-2016) breeding data. Video systems were used at colonies in 2015 and 2016 to determine causes of nest failure. No differences in breeding parameters were found between removal periods, however video data confirmed nest predation as the primary cause of nest failure. Laughing Gull (Leucophaeus atricilla) was the top predator and accounted for 63% of all detected predation events. In 2015, video monitoring identified a novel predator, exotic and invasive nutria (Myocastor coypus), that were responsible for 43% of predation events. In 2016, following a 280% increase in nutria removal from 2015, no nutria predation was recorded.

Adult piping plover habitat selection varies by behavior

AbstractPiping plovers (Charadrius melodus, “plover”) are beach‐nesting shorebirds that occupy their breeding range from about April to August. When plovers arrive on the breeding grounds, they select and defend territories, lay and incubate eggs, and tend to precocial broods; additionally, adults can return to a non‐breeding stage after final nest failure or after chicks have fledged or died. We hypothesized that habitat selection would differ among these phases of the breeding cycle because the needs of the birds differ among them. We monitored plovers on Fire Island and Westhampton Island, New York, during 2016–2018, recording individual locations of adult birds. We used resource selection functions to determine whether breeding stage (pre‐breeding, nesting, brooding, post‐breeding), breeding status (breeding, non‐breeding), or instantaneous behavior class (parental [incubating, brooding, and accompanying chicks], non‐parental [all other behaviors]) best explained relationships with landscape characteristics known to be important to breeding plovers. Differences in habitat selection between adults exhibiting parental behaviors and non‐parental behaviors had the greatest support in our model set. Compared with non‐parental plovers, plovers displaying parental behavior selected areas closer to bay intertidal habitats and with proportionally more dry sand in the surrounding landscape than other habitat types. Non‐parental plovers avoided areas with more dry sand and did not select for or against bay intertidal habitats. Additionally, non‐parental plovers avoided development and higher elevation areas more than parental plovers, although both exhibited avoidance of these features. The total amount of suitable habitat ranged from 100.14 ha to 151.07 ha. In each year, there was more suitable habitat for parental plovers (129.57–151.07 ha) than non‐parental plovers (100.14–108.83 ha). Due to these differences, when improving, creating, and protecting plover habitat, managers should consider habitat needs of both behavioral classes. Habitat management for nesting and brooding plovers should focus on maintaining vegetation‐free sand and access to foraging habitat, and habitat management for non‐parental plovers should focus on flat, low‐elevation foraging habitats, particularly areas further from development.

Reactions of breeding common swifts (Apus apus) to explosions

Sonic booms or disruptive explosions cause differing response in wildlife. In May 2021, when missiles were fired at urban areas in Israel, we observed the responses of breeding common swifts (Apus apus). In both nests, the initial boom resulted in a startled awakening of the swifts. In one case, a parent engaged in displacement behaviour of feeding the young while in the second case a parent tried to clamber up the walls. Our data support earlier studies that although auditory booms are disruptive, they do not result in nest abandonment or nest failure.

Fine-scale plasticity in nest placement can compensate for poor quality junipers as nesting trees for gray vireos.

Understanding the interactions between behavior and habitat characteristics can have important implications for species of conservation concern. Gray vireos (Vireo vicinior) are one example of a species of conservation concern that is understudied in terms of nest survival probabilities and the habitat characteristics that influence them. Our objective was to determine if habitat features such as juniper density, juniper foliage density, or tree height influence nest survival probabilities, and if gray vireo nest placement can mitigate habitat risks. Based on previous work, we expected daily nest survival probabilities to be associated with nest height and surrounding vegetation. We monitored 89 nests in central New Mexico from 2016–2018 to estimate daily nest survival probabilities. We compared variation in nest placement, nest tree characteristics, and surrounding vegetation between failed and successful nests using logistic exposure models and Akaike Information Criteria. Daily and cumulative nest survival probability were 0.983 (95% CI [0.973–0.989]) and 0.575 (95% CI [0.444–0.702]), respectively. Top models predicting nest survival included a negative interaction between nest-tree foliage density and the distance of the nest from the edge of the nesting tree. This suggests that gray vireos can mitigate risks associated with low nest concealment by nesting closer to the interior of the nesting tree.

Nest survival of Seaside Sparrows (Ammospiza maritima) in the wake of the Deepwater Horizon oil spill.

In 2010, the Deepwater Horizon oil spill released an estimated 4.9 million barrels of oil into the Gulf of Mexico, damaging coastal ecosystems. Seaside Sparrows (Ammospiza maritima)—a year-round resident of Gulf Coast salt marshes—were exposed to oil, as shown by published isotopic and molecular analyses, but fitness consequences have not been clarified. We monitored nests around two bays in Plaquemines Parish, Louisiana, USA from 2012–2017 to assess possible impacts on the nesting biology of Seaside Sparrows. A majority of nests failed (76% of known-fate nests, N = 252 nests, 3521 exposure-days) during our study, and predation was the main cause of nest failure (~91% of failed nests). Logistic exposure analysis revealed that daily nest survival rate: (1) was greater at nests with denser vegetation at nest height, (2) was higher in the more sheltered bay we studied, (3) decreased over the course of the breeding season in each year, and (4) was not correlated with either sediment polycyclic aromatic hydrocarbon concentrations or estimated predator abundance during the years for which we had those data. Although the Deepwater Horizon spill impacted other aspects of Seaside Sparrow ecology, we found no definitive effect of initial oiling or oiled sediment on nest survival during 2012–2017. Because predation was the overwhelming cause of nest failure in our study, additional work on these communities is needed to fully understand demographic and ecological impacts of storms, oil spills, other pollutants, and sea-level rise on Seaside Sparrows and their predators.

Time heals: Boosted breeding seabird populations on restored Cousine Island, Seychelles

AbstractHistorically, Cousine Island was used for agriculture and harvesting various seabird eggs, but following restoration efforts initiated in the 1990s, it has become an important nesting area for Seychelles seabirds. White‐tailed tropicbird (Phaethon lepturus), white tern (Gygis alba), and lesser (Anous tenuirostris) and brown noddy (Anous stolidus) populations were monitored on Cousine Island between 1997 and 2017 to determine the long‐term population responses to various environmental variables during the winter breeding season. White tern, brown noddy, and white‐tailed tropicbird populations are increasing, indicating that island conditions for breeding have improved for these species in the last 20 years. Lesser noddy populations are in decline, but not significantly, with winter air temperature significantly adding to this trend. Lesser noddies are true colonial nesters and are therefore potentially more affected by climatic conditions that result in nest failures and nearshore prey shortages. The relationship between numbers of seasonally breeding species (lesser and brown noddies) and those of year‐round breeders (white‐tailed tropicbirds and white terns) was also examined. Brown noddy population trends significantly predicted white‐tailed tropicbird and white tern winter breeding population trends, suggesting that these species populations respond similarly to local conditions. Data from this study establish a baseline for future population trend investigations and assessments of island conservation and management success.