Nest Placement Research Articles

Effect of artificial fish nest placement on spawning site preference and reproductive efficiency in reservoir fish with adhesive and demersal eggs

Artificial fish nests are common tools in fisheries management, providing spawning grounds to enhance the size and diversity of fish populations. This study aimed to explore the effects of deployment locations on the reproductive efficiency and preferences of fish with adhesive and demersal eggs using artificial nests. Floating artificial nests were deployed in three regions (upstream, midstream, and downstream) of a reservoir in Zhejiang, China, at locations with three topographical types: steep slope (reservoir shore, slopes > 60°), gentle slope (reservoir shore, slopes < 30°), and confluence (middle thread of channel). The quantity, viability and species of eggs in artificial nests were recorded throughout the fish reproductive cycle. The mean density of viable eggs in artificial nests in the midstream region (1176 ± 448 ind./m2) was significantly higher than that in the downstream (477 ± 167 ind./m2) and upstream regions (350 ± 148 ind./m2). The survival rate of fish eggs in the gentle slope area (56.94 ± 11.97%) was significantly lower than that in the confluence (79.80 ± 6.20%) and steep slope areas (74.47 ± 11.40%). Different fish groups respond uniquely to environmental factors. We suggest that the construction and implementation of artificial nests should be based on the differences in upstream and downstream water bodies, as well as the specific ecological requirements of target fish species. Management practices should focus on site-specific environmental monitoring and adapt nest placement to optimize conditions for different species. Furthermore, future research should aim to develop predictive models that integrate environmental factors and species needs, providing a more robust basis for artificial nest placement and fisheries management.

Nesting density and nest site selection of the Magpie Pica pica in Kaliningrad, south-east of the Baltic Sea area

Over the past decades, the Magpie, which has ecological and behavioral flexibility, has colonized many cities. In this study, we examine the effect of urban disturbance on nesting density of the Magpie and nest height in a city in the south-eastern Baltic region. The studies were carried out in Kaliningrad (54°43’N, 20°30’E) during the leafless period in 2018–2021 in green residential areas with a predominance of 5-storey buildings (“residential area”) and low-rise individual housing areas (“individual houses”). In the residential area, nest counts were carried out separately in the central part of the city and outside the city center. Based on literature data on urban populations of the Magpie in other cities, we predict that: (1) in the central part of the city there will be a higher nesting density of magpies and (2) in the central part of the city, nests will be located higher than outside the central part of the city. The results obtained did not confirm these assumptions. The average nesting density in residential areas in the city center and outside the city center was virtually the same. And, in addition, in the residential area in the city center, nests were on average located lower than in the residential area outside the central part of the city, but the differences were not statistically significant and the median values of these city zones coincide. The work also provides data on the placement of nests on various types of trees and shrubs. The Hooded crow, being the main predator and competitor of the Magpie, shares the same habitats in Kaliningrad. This coexistence could potentially slow down the increase in Magpie nesting density, especially in the residential area of the city centre, where the nesting density of the Hooded crow is significantly higher than outside the city centre.

The win-stay, lose-switch renesting strategy of a territorial bird endemic to subtropical salt marshes

IntroductionThe “win-stay, lose-switch” (WSLS) strategy used by birds involves decisions to maintain or alter the characteristics of the subsequent nest according to the outcome of the previous one. In salt marshes, nest failure occurs due to flooding, predation, or tipping, creating a trade-off for nest placement: it should be low enough to avoid predators from above and tipping by the wind, and high enough to avoid flooding. In salt marshes of Southern Brazil, predation from above is carried out by rails that also prey on nests from below, promoting nondirectional pressure capable of neutralizing bird responses. We aim to test the WSLS strategy and to assess its adaptive significance for Formicivora acutirostris, the only thamnophilid endemic to salt marshes. Our general premise is that the adoption of the WSLS strategy would vary in response to the fate of the previous nest, considering also the environment type.MethodsWe evaluated the fate, environment type, height, altitude, and thickness of nests of F. acutirostris in southern Brazil, between 2006 and 2023. We assessed the effects of the nest attributes, tested the adoption of the WSLS strategy, and explored its adaptive significance using generalized linear mixed models. We also examined the influence of factors such as nest environment, nesting timing, and pair age on nest fate and parental behavior.ResultsWe studied 98 renesting cases. Flooded nests were at a lower height than predated, tipped, and successful nests, and tipped nests were thicker than flooded and successful nests. Nest heights differed among environment types. The species adopted the WSLS strategy by increasing nest height after flooding, but we do not support its adaptive significance. No additional factors influenced the behavior of the species.DiscussionAlthough the adoption of the WSLS strategy by F. acutirostris was confirmed regarding the increase in nest height after flooding, it did not result in a significant increase in reproductive success, suggesting that other pressures, such as predation and tipping, are limiting the adaptive potential of this strategy. We emphasize the threat of the high reproductive failure for the conservation of F. acutirostris and proposes reducing predation pressure as an important conservation strategy.

Погляд усередину: гніздові матеріали і деякі закономірності гніздової біології коноплянки Linaria cannabina (Linnaeus, C 1758) на Львівщині

The article deals with some aspects of the nesting biology of Linnaria cannabina (Linnaeus, C 1758) in Lviv region. The question of placement, the composition of the nests and the factors that affect this is revealed. The material for writing this article was the data of the Bank of bird nests of Western Ukrainian Ornithological Society (ZUOT) (n=181) and own data (n=18) for 40 years (from 1973 to 2012). Nests were collected in different biotopes and, depending on the distance to the human settlement, were divided into three groups (within settlements, on their outskirts and far beyond in natural biotopes). It was found that for the placement of nests, the common linnet often chooses coniferous (mainly young spruce, thuja or juniper). Among deciduous found trees, a significant variety of bushes and twisted vines (ivy). To choose a place for linnet nest, the architectonics of the aboveground part of the plant is important, so even trees were chosen that are similar to bushes. Very often common linnet places nests in various hedges (spirea, acacia yellow, etc.). Probably due to the fact that the nest is well disguised, its placement height is small (0.2–2.2 m, on average 1.10±0.03 m). The main materials that L. cannabina chooses to build nests are typical of birds of this species in Europe. Linnet nests consisted of plant (in 100 % of the studied nests), animal (98.4 %) and sometimes (23.2 %) materials of anthropogenic origin. From plant materials, linnet most often chose for the nest the roots and stems of herbaceous plants, less often the branches and leaves of trees, plant fluff and moss. Among the materials of animal origin, animal hair and bird feathers were often found in the lining of the nest. Some of the nests contained components of anthropogenic origin (СAО) in different quantities (most often cotton wool). The basic nesting materials of the linnet in Lviv region were small roots and stems of single- and dicotyledonous herbaceous plants, and in the inner part – hair of mammals, feathers of birds, cotton wool. The presence of CAO in bird nests depends on the distance to human settlements and the time of nest construction. In the last couple of decades, the frequency of use of CAO in the nests of the linnet has increased rapidly, which may indicate a growing environment pollution, as well as, perhaps, the habituation to use such materials by common linnet.

Nest placement accounts for thermal exposure secondarily: insights on multifarious selection

Nest placement accounts for thermal exposure secondarily: insights on multifarious selection

Habitat preferences of breeding Eurasian Sparrowhawks Accipiter nisus in Central Europe

ABSTRACT Capsule A description of habitats used for breeding by Eurasian Sparrowhawks, along with variables affecting their breeding habitat selection. Aims To describe the habitat preferences of breeding Eurasian Sparrowhawks, and to identify variables affecting their breeding habitat selection at different spatial scales, in a rural area of Central Europe (Czech Republic). Methods Eurasian Sparrowhawk nests were found and the habitat characteristics of breeding sites were measured at three spatial scales, and then compared with randomly selected locations. Results The nests were regularly distributed within the forests of the study area, avoiding small forest patches. The territories were somewhat associated with dense forest stands of a distinctive structure. All nests were built in coniferous trees, in the lower parts of their green crowns and close to the trunks. In the areas surrounding the nests, we found a greater abundance of some bird (prey) species and a higher diversity of birds, compared to the random areas. Conclusion The Eurasian Sparrowhawks preferred to breed in forests with a specific structure that provided sufficient concealment and access to their nests, and they located their breeding territories as far from each other as possible. The birds also seemed to prefer breeding in localities with a greater food supply. The variables affecting Eurasian Sparrowhawk breeding habitat selection may include intraspecific competition, size and structure of available forests, availability of coniferous trees for nest placement, and the composition of the food supply in the vicinity of their nests.

New data on the nesting sites selection and breeding success of three bird species in the riparian vegetation of Northwest African rivers

Many avian species partition feeding and breeding resources to avoid competition for nesting and food elements. This competition frequently leads to the segregation of space and time use among cohabiting species. The breeding requirements of coexisting species and drivers of segregation are poorly understood in passerine birds. In this study, we monitored nesting habitats, nest placement, and breeding success among two passerine birds, Hippolais polyglotta and Turdus merula, and the Columbidae species Streptopelia turtur arenicola, in rivers of the upper Moulouya (Morocco) Mountains to examine the levels of habitat partitioning, success rates, and governing factors during the breeding season. We recorded the nests, nesting sites, nest placements, and success rates of the studied species along three rivers during 2017 and 2019. Our results revealed important breeding activity in the studied birds, with 420 nests of H. polyglotta and 88 nests of T. merula, compared to 99 nests of S. t. arenicola. Nest niches were segregated between passerines and Columbidae and within passerines. Nesting sites were segregated along sections of rivers except for nests of H. polyglotta, which were shared between upstream and intermediate zones. Nest substrates were partially segregated among the three species; nests of H. polyglotta and S. t. arenicola were commonly constructed on Crataegus monogyna and Rosa canina substrates, while nests of T. merula were on Salix sp. Similarly, vertical placements of nests were segregated among birds. Breeding success rates differed among birds (94.44% in T. merula, 87.88% in H. polyglotta, and 55.56% in S. t. arenicola) due to human and natural factors. Finally, this study confirmed the first breeding case of H. polyglotta on the southern slope of the Mediterranean and provided new insight into nest niches in cohabiting passerines and Columbidae species cobred in riparian vegetation in Morocco and the entire region of North Africa. However, future investigations are required to understand the main reasons behind the selection of nesting habitats for passerine species, particularly in farmlands.

Fieldfare (Turdus Pilaris L.) Nesting Ecology in the City of Stepanakert of the Republic of Artsakh and its Surrounding Territories

The present study delves into the nesting ecology of fieldfares within the avian population of Stepanakert, located in the Republic of Artsakh, alongside its contiguous regions. The research material encompasses observations and investigations carried out between 2017 and 2022 within the aforementioned geographic domains. In our specific conditions, the initiation of the fieldfare nesting process transpires under outdoor air temperatures exceeding +8°C to +10°C, while the first appearance of an egg within the nest during spring corresponds to temperatures of +15°C to +16°C. The nesting substrates encompass an array of broad-leaved and coniferous trees, in addition to various man-made structures. Nest placement exhibits diversity, situated at elevations of 0.5-1.2 meters above the ground within open areas proximate to the city, escalating to 3-4.5 meters within the central zones of Stepanakert, and subsiding to 1.5-2.5 meters in woodland environs adjacent to the city. The construction of nests unfolds over a median period of 5-7 days. On average, nests accommodate a clutch of 3-5 eggs. The morphological attributes of eggs reveal considerable variability. In our contextual setting, fieldfares engender two generations annually, with an incubation duration spanning 12-13 days. Hatchlings emerge from eggs within a single day, occasionally within two days, eventually taking their inaugural flights after 15-17 days. The percentages of losses occurring between the embryonic stage and the attainment of flying capability among chicks display distinct variations.

Forty years of monitoring increasing sea turtle relative abundance in the Gulf of Mexico

Longitudinal data sets for population abundance are essential for studies of imperiled organisms with long life spans or migratory movements, such as marine turtles. Population status trends are crucial for conservation managers to assess recovery effectiveness. A direct assessment of population growth is the enumeration of nesting numbers and quantifying nesting attempts (successful nests/unsuccessful attempts) and emergence success (number of hatchlings leaving the nest) because of the substantial annual variations due to nest placement, predation, and storm activity. We documented over 133,000 sea turtle crawls for 50.9 km of Florida Gulf of Mexico coastline from 1982 to 2021 for a large loggerhead turtle nesting aggregation and a recovering remnant population of green sea turtles. Over time both species have emerged to nest significantly earlier in the year and green sea turtle nesting seasons have extended. Nest counts and hatchling production for both species have significantly increased, but the rate of emergence success of hatchlings leaving nests has not changed for loggerheads and has declined for green sea turtles. Sea level rise and coastal developments undoubtedly influence coastal habitats in the long-term, impacting nest site selection and potential recruitment from the loss of emerged hatchlings. However, the present indications for steady Gulf of Mexico recovery of loggerhead and green sea turtles counter findings of the Florida Atlantic coasts. This study indicates that effective conservation practices can be detected within time scales of 1–2 turtle generations.

Hygiene of maintenance of song and decorative birds

The article presents data on the study of modern methods of keeping song and ornamental birds at home. Creation of optimal microclimate parameters for birds based on their families and species. Creating increased attention to acquainting people with the world of song and ornamental birds and ways to attract them through the thoughtful placement of artificial nests in apartments, courtyard parks and gardens, competent feeding of birds in different seasons of the year in the general context with environmental issues in large metropolitan areas. Keeping and breeding song and ornamental birds at home makes it possible to preserve many species, and with proper care and feeding, birds live in captivity for a long time and breed well.

Пространственное распределение гнёзд врановых птиц (Corvidae) в компонентах урбанизированной среды (на примере Кировского района г. Саратова)

This study is dedicated to the nest placement peculiarities of four species of the Corvidae family: the Jackdaw, Rook, Hooded Crow, and Eurasian Magpie – in the urbanized environmental components on the territory of the Kirovsky district of Saratov. The following methods were used in the work: route and areal accounting, cartographic modelling, plotting isolines based on cartographic data, assessing the reliability of differences in the number of corvid nests using Pearson’s chi-squared test, determining the rate of urbanization of various areas of the model area based on the method used by E. L. Lykov, assessing the dependence of the number of nests on the rate of the territory urbanization using Spearman’s correlation coefficient. The distribution of 652 nests according to the biotopes was analyzed, the assessment of the corvid nesting density in various urban environmental habitats was carried out. The nest placement density reaches its maximum in the areas with abundant green places, a large number of nesting sites, both of natural and anthropogenic origin and low rate of human disturbance, being in the areas with low-rise buildings, in the forest belts, in the natural park “ Kumysnaya polyana”and in the old Voskresenskoe cemetery. The Jackdaw and the Rook are the most selective for breeding sites species, their nests being located in human buildings and on closely placed tall trees. The Hooded Crow nests most evenly and successfully occupied the habitats of Saratov. The Magpie’s nesting areas are more associated to large groups of woody vegetation, the highest density of its nest placement was observed in the natural and natural-anthropogenic components of the urban environment. The negative relation between the quantity of nests of the two species – the Hooded Crow and the Magpie – and the rate of the territory urbanization was revealed. The nesting of the Jackdaw and the Rook are affected mostly not by the urbanization rate, but the availability of breeding sites.

The Effect of Floods on Nest Survival Probability of Common Sandpiper Actitis hypoleucos Breeding in the Riverbed of a Large Lowland European River

The natural valleys of large rivers provide suitable nesting and foraging sites for many bird species. In this study, we assess the effects of water fluctuations during the breeding season on Common Sandpipers’ nest survival on a semi-natural section of the Vistula River, and evaluate which tactics this species can adopt to minimise the effects on a long-term scale. Birds can avoid losses due to flooding by adjusting the timing of nesting to avoid the occurrence of extreme water conditions, and/or by choosing a safe nesting location. We found that nest location is a direct response to periodic high water, and the threat of flooding seems to be one of the important determinants of Common Sandpiper nest placement. The choice of nest location is not random, as 70% of pairs nested above a height that provides an 80% chance of avoiding flooding of the nest. For the lowest-lying nests found in this study, nesting success was reduced up to 92% because of inundation. Birds choose more elevated places, even during the second half of the season when the threat of flooding is lower. Their preference for nesting above a certain height does not change over the breeding season, which corresponds to the very small impact of the date of first egg laying on breeding success. Those who breed earlier in the season have a slightly higher risk of being flooded, but nesting in more elevated places reduces this risk much more than shifting the time of breeding.

Nest predation in Patagonian wetlands: predator assemblage and microhabitat characteristics

ABSTRACT Multiple factors influence predation risk, ranging from habitat conditions to the composition and behaviour of predators. Although these factors are well documented for forest ecosystems, there is little evidence for wetlands, especially within Patagonia. Using artificial nests and camera traps, we documented the nest predation rates and predator assemblage of birds nesting in wetlands of the Patagonian steppe. We also determined the effect of vegetation cover on nest survival and studied the variation in predator groups according to nest placement: nests located in an open wetland, peripheral grassland to the wetland, and nests located in shrubs at different heights. We found 84% of nests failed, counting birds, mice, and armadillos as the main predators. Vegetation cover affected predation events of birds and small mammals, but not those of larger mammals. In turn, small mammals preyed on nests exclusively located in peripheral grassland, medium mammals preferred nests placed in open wetlands, and predation by birds was irrespective of open wetlands and grassland. We also found differences in nest predator assemblage between nests placed on the ground and in shrubs, with birds being the main predators of nests located above ground. These results can be attributed to differential habitat use and movement patterns specific to each predator group. Therefore, the identity, density, and behaviour of predators should be taken into account when planning conservation strategies for birds breeding in wetlands.

Female Grass Wrens adjust brooding effort according to ambient temperature, male feeding contribution and nest placement

The keystone of life‐history evolution theory proposes a trade‐off between current reproductive effort and future survival. Brooding is an essential and often overlooked component of parental behaviour of altricial birds intended to transfer heat to nestlings. Brooding under challenging environmental conditions can be energetically demanding and may adversely affect adult survival and future reproduction. We provide the first detailed description of the brooding behaviour of a south temperate grassland specialist: the Grass Wren Cistothorus platensis. In Grass Wrens, both sexes collaborate in parental care; however, only females brood the nestlings. We examined the relationship of ambient temperature, male feeding contribution, nestling age, nest size and nest placement in determining brooding behaviour. Additionally, we evaluated the effects of brooding behaviour on nestling body condition near fledging and female apparent survival. Brooding effort decreased with nestling age. Females increased their brooding effort at low ambient temperature and when males delivered more food. At lower ambient temperatures, females increased brooding effort in nests placed further from plant edge, with taller plant heights and well‐concealed substrates. However, there was no relationship between brooding effort and nest size. Neither female investment in brooding nor the number of nestlings produced per female was associated with nestling body condition near fledging or female annual apparent survival. Our results identify several factors that shape brooding behaviour in this south temperate passerine, suggesting that females favour nestling thermal conditions under adverse weather conditions.

Woody plant encroachment reduces density of most grassland specialists in a desert grassland but has limited influence on nest survival

AbstractWoody plants are proliferating in grassland ecosystems worldwide, altering distributions and demography of many imperiled species. The transition from grassland to shrubland is especially prevalent in semiarid regions, but the influence of woody plant encroachment (WPE) on birds that breed in desert grasslands is poorly understood, which reduces the potential for developing effective conservation actions for this imperiled group. During 2013–2015, we surveyed breeding birds on 140 10-ha plots in southeastern Arizona, USA, that spanned a gradient of encroachment (0–37% cover) by Prosopis (mesquite), which has invaded grasslands worldwide. We evaluated the effect of WPE on density, nest placement, and nest survival at 3 spatial scales (within 1.5 m and 5 m of the nest and at the 10-ha plot) for common species and 3 species groups: obligate grassland specialists (n = 7 species), facultative grassland specialists (n = 17), and species not typically associated with grasslands (n = 42). Density of the obligate species group decreased by 30% across the gradient of shrub (0.5–2 m tall) cover and by 23% across the gradient of tree (&amp;gt;2 m tall) cover. For 3 of 4 obligate species, density decreased by ≥50% when tree cover increased from 0 to 15%. In contrast, density of the facultative species group nearly tripled as tree cover increased from 0 to 22%. Obligate species placed nests 3.5 times farther from trees than facultative species (51.9 vs. 14.8 m). WPE influenced nest survival for 2 species but effects were inconsistent across spatial scales: nest survival of Grasshopper Sparrow (Ammodramus savannarum) decreased with increasing cover of trees on plots and shrubs within 5 m of the nest, and nest survival of Mourning Dove (Zenaida macroura) increased with increasing cover of shrubs on plots. Our results demonstrate that many grassland obligates are affected adversely even by small increases in woody cover. Consequently, restoration efforts should focus on early stages of WPE (i.e., cover &amp;lt;10% and shrubs &amp;lt;2 m tall) when removal of woody plants is more effective and less expensive relative to later stages.

Drones and Bathymetry Show the Importance of Optimal Water Depth for Nest Placement Within Breeding Colonies of Western and Clark’s Grebes

Drones and Bathymetry Show the Importance of Optimal Water Depth for Nest Placement Within Breeding Colonies of Western and Clark’s Grebes

Nest-platform, nest-tree, nest-site, home-range and landscape characteristics of the Lesser Spotted Eagle (Clanga pomarina) in relation to its breeding performance in East Carpathians

Habitat loss and fragmentation along with altered disturbance regimes cause raptor population declines, but processes, rates and interactions are seldom known. Knowledge gaps remain mainly in large forest-dwelling raptors that use habitats on several spatial scales. Our study focusses on breeding habitats and habitat-associated breeding performance of the Lesser Spotted Eagle (“eagle”) across five spatial scales in Laborecká vrchovina Mts (East Carpathians, Slovakia) during 2011–2016. We calculated two relative measures of breeding performance (breeding attempt index, BAI; nest productivity index, NPI) and related them to habitat characteristics sampled on the nest-platform, nest-tree, nest-site, home-range and landscape scale. We found that eagle‘s breeding performance was best explained by predictors on the home-range and landscape scale. BAI and NPI strongly and consistently increased with increasing distance of nest to the nearest felling site and with occurrence of the nest site on lower slope landforms. Former finding supported ample evidence that logging operations pose agrave threat to eagle’s reproduction, while the latter hinted at its strong preference or even specialization for forest edges, for notably old regional ecotones between montane forests and submontane non-forest formations show lower slope topography. On the nest-site scale, nest productivity (NPI) significantly and strongly increased with increasing percentage of Sessile Oak (Quercus petraea) and decreased with cosine of slope aspect in response to more open and accessible canopy structure resulting from oak appearance in beech-dominated forests and to contrasts in solar radiation, shade and similar north–south effects. On the nest-platform and nest-tree scale breeding performance marginally significantly increased with increasing relative nest height above ground and decreased in nests of natural origin (in BAI). It pointed to unrecognized relevance of relative nest height that may link nest-tree with nest-site scale and reflect atrade-off between nest accessibility and nest protective cover, and to greater nest placement diversity with possible greater vulnerability of natural nests. Differences in breeding performance measured by BAI vs NPI indicated that certain selection pressures may vary significantly during the breeding cycle, e.g., early vs late breeding failures and subsequent learning from negative experience. We recommended several management actions by our results, particularly to advance systematic eagle monitoring, to address multiple scales of its habitat use according to their relative importance, to increase the width of protection zones around nests and adopt new or strengthen existing landscape-scale measures and to follow sustainable forestry as apart of integrated landscape management instead of close-to-nature forestry.

ASSESSMENT ON THE PARENTAL CARE STRATEGY OF THE YELLOW-VENTED BULBUL PYCNONOTUS GOIAVIER IN PERAK, MALAYSIA

The parental care strategy and diet requirements of the yellow-vented bulbul Pycnonotus goiavier chicks were studied. The assessment was conducted based on the (1) number of feeding bouts (bouts/hour), (2) average time intervals between each feeding (minutes/bouts) (3) feeding strategies (perch-go-in or direct-go-in) and (4) types of food items carried to the nest to feed the chicks. A total of 6000 minutes of direct observation from a close distance was performed for 10 days from 28th May 2016 until 6th June 2016 between 0700-1900 hours. Out of 816 independent feeding bouts, the parents preferred the perch-go-in (80.03%) as compared to the direct-go-in (19.97%) feeding strategy to feed the chicks in their nest. The average time spent for feeding was 7.50 ± 3.84 minutes / bout (7.50 ± 1.23 bouts/h), with the least number of bouts during the morning feeding time at 5.68 ± 3.09 bouts/h. The most frequent food items comprised of invertebrates such as dragonflies (16.15%) and grasshoppers (11.35%) and fruits including Murraya koenigii (14.02%). The success of raising both the chicks depended on the nest placement, feeding strategy, food availability, predation risk and commitment of both parents. Keywords: life history, feeding bout, food types, chicks, activity pattern

Habitat edges influence the distribution of nest predators for Seaside Sparrows, but not nest placement or success

Abstract Nest failure for coastal marsh bird species is primarily caused by predation and nest flooding. As sea level rise makes nest flooding more likely, the threat of nest predation will constrain the potential adaptive responses of marsh nesting species. Thus, understanding the predictors of nest predation is important for the conservation of salt marsh-dwelling bird species, such as the Seaside Sparrow (Ammospiza maritima). Predator activity may be influenced by landscape features (particularly habitat edges), potentially making nest predation predictable. We aimed to understand the predictability of Seaside Sparrow nest predation relative to two major landscape features: roads and tidal rivers, as both of these edges may be entryways or attractants for predators in marshes. In coastal Georgia, USA, we assessed mammalian predator activity relative to the two features of interest, and hypothesized that mammalian predator activity would be greater close to roads and tidal rivers. We also recorded Seaside Sparrow nest locations and nest predation events and hypothesized that nest predation events would increase with increasing predator activity. Consistent with our first hypothesis, mammalian predator activity increased close to roads and tidal rivers, but mammalian predator distribution did not explain the spatial variation in Seaside Sparrow nest predation thus not supporting our second hypothesis. Seaside Sparrows also placed their nests in locations with high mammalian predator activity, indicating that the ability to avoid nesting in high-risk areas may be constrained by habitat or resource limitations. Additionally, mammals may not be the primary nest predators, as we found that one bird species—Marsh Wren (Cistothorus palustris)—contributed substantially to nest predation rates. Understanding the predictability of mammalian predator distribution can allow for focused predator management efforts, such as exclusion, to habitat edges where we found the highest mammalian predator activity, which could relax the constraint of nest predation on Seaside Sparrow’s ability to respond to the intensifying threat of sea level rise.

The location of thrush nests on buildings affects the chance of cowbird parasitism

Nest site placement is a critical choice among passerines, being an important factor that affects their breeding success. In urban areas, human buildings offer suitable nesting sites usually less exposed to predators and brood parasitic birds and readily available to be reused for several breeding seasons. However, the extent to which the features of nest placement sites in buildings contribute to reduce nest detectability by predators and brood parasites is still unknown. Here, we tested whether the features of the nesting site (i.e., lateral concealment, distance to the building ceiling, and height above ground) affect the chance of brood parasitism by Shiny Cowbirds (Molothrus bonariensis) in Pale-breasted Thrushes (Turdus leucomelas) nests placed on buildings in a Brazilian suburban area from 2013 to 2019. Cowbird parasitism increased throughout the study years, and nests closer to ceilings, supposedly better concealed, were more likely to be parasitized. Laying date, height above ground, and lateral concealment were not related to the probability of cowbird parasitism. We suggest that less concealed nests enhance vicinity monitoring by parents, allowing a faster agonistic response to the presence of cowbirds near the nest. Our results indicate that nest site location in cities may have consequences for the breeding success of cowbird hosts.