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The use of open cup nests by birds for roosting during the non-breeding season is a poorly documented yet intriguing phenomenon. Here, I describe the use of old Barn Swallow (Hirundo rustica) nests as winter roost sites by Dark-eyed Juncos (Junco hyemalis) as well as agonistic interactions at these structures. In 2016–2023, I observed juncos roosting in four Barn Swallow nests in New Jersey, USA, and used digital video to closely monitor activities at one nest. A junco roosted at the monitored nest on 56 of 71 nights, entering the roost 71 ± 26 min before sunset (mean ± SD; range: 20–168; n = 54) and exiting 27 ± 5 min before sunrise (range: 7–32; n = 43). In spring, a pair of House Finches (Haemorhous mexicanus) began preparing the swallow nest for egg laying during the day while a junco still slept there nightly. The House Finches increasingly came into conflict with the roosting junco, evicting it at least temporarily on nine evenings despite efforts by the junco to defend the site. Similar agonistic encounters with three other juncos, three unidentified birds, and a Carolina Wren (Thryothorus ludovicianus), which also roosted in the Barn Swallow nests, were documented but did not result in eviction. Winter roosting in open cup nests appears to be rare in birds despite potential thermal benefits. The occupancy rate and tenacity observed at the monitored Barn Swallow nest suggest that open cup nests may be desirable roost sites, and that the phenomenon deserves further study. Un fenómeno poco documentado pero intrigante es el uso de nidos de tipo ‘taza abierta’ por las aves para pernoctar, durante la época no reproductora. Aquí describo el uso de viejos nidos de la golondrina Hirundo rustica como dormideros de invierno por el junco Junco hyemalis, así como las interacciones agonísticas en estas estructuras. En 2016–2023, observé a Junco hyemalis pernoctar en cuatro nidos de Hirundo rustica en Nueva Jersey, Estados Unidos, y utilicé vídeo digital para seguir de cerca las actividades en un nido. Un individuo de Junco hyemalis durmió en el nido monitoreado en 56 de las 71 noches, entrando en el dormidero 71 ± 26 min antes de la puesta de sol (promedio ± DE; rango: 20–168; n = 54) y saliendo 27 ± 5 min antes del amanecer (rango: 7–32; n = 43). En la primavera, una pareja de pinzones Haemorhous mexicanus empezó a preparar el nido de Hirundo rustica para la puesta de huevos durante el día, mientras que un individuo de Junco hyemalis siguió durmiendo allí por la noche. Los individuos de Haemorhous mexicanus entraron cada vez más en conflicto con el individuo de Junco hyemalis, desalojándolo al menos temporalmente en nueve noches a pesar de sus esfuerzos por defender el lugar. Se documentaron encuentros agonísticos similares con otros tres individuos de Junco hyemalis, tres pájaros no identificados y una ratona Thryothorus ludovicianus, que también pernoctó en nidos de Hirundo rustica, pero estas interacciones no acabaron en desalojo. El pernocte invernal en nidos del tipo taza abierta parece ser poco frecuente en las aves a pesar de sus posibles beneficios térmicos. La tasa de ocupación y la tenacidad observadas en el nido de Hirundo rustica objeto de seguimiento sugieren que los nidos del tipo taza abierta pueden ser lugares de descanso deseables, y que el fenómeno merece estudios más profundos. PALABRAS CLAVE estructuras antrópicas; competencia entre las aves; reutilización de nidos; comportamiento novedoso; invierno; dormir

Due to rapid homogenization in habitat types as a result of urbanization, some urban birds adapt their nesting strategies to changes in local habitat characteristics. Bird nesting decisions might have been mainly linked to resource constraints and ensuring reproductive success. In this study, we examined patterns of nesting behavior by spotted doves (Spilopelia chinensis) in a rapidly urbanizing area of Nanchang, China using ArcGIS 10.8, satellite tracking, camera traps, and field survey. To explore the mechanisms underlying nesting behavior in urban habitats, we assessed the correlations between nest reuse and reproductive success, and between nest reuse and nest predation. From December 2018 to December 2021, a total of 302 breeding nests were surveyed. The results revealed that the nest reuse rate was 38.08% (n = 115). Nests closer to trunk, with lower nest position and higher large‐scale urbanization score tended to have higher reuse rate. In addition, nests with the higher the nest height and percent of canopy cover, and the lower small‐scale urbanization score were more likely to reproduce successfully, and the reused nests also reproduce more successfully. The reproductive success associated with nest reuse was significantly higher than that associated with new nests (χ2 = 8.461, p = .004). High degree of urbanization promoted nest reuse of spotted doves (large‐scale urbanization score, z = 2.094, p = .036), which apparently enhanced their reproductive success (nest reuse, z = 2.737, p = .006). In conclusion, a nest structure with good permeability is the material basis for the nest reuse in spotted dove, while the relatively low risk of predation in urban habitat and the scarcity of nest site resources due to urbanization increase the tendency of birds to reuse old nests, which is associated with their reproductive success and evolutionary fitness. High degree of urbanization promoted nest reuse. Nest reuse enhances avian reproductive success. Nest reuse did not increase the risk of predators.

Nest-switching is an important breeding strategy for multiple-brooded bird species. When deciding whether or not to switch nests for subsequent breeding attempts, pairs must weigh the costs and benefits of various factors related to the number of fledglings of the first breeding attempt, the likelihood of nest predation, and qualities of the nest environment, such as nest ectoparasites and the age of the nest. In this study, we analyzed the predictors and consequences of nest-switching behavior at 6 breeding sites of North American Barn Swallows (Hirundo rustica erythrogaster), where 60% of pairs that raised 2 broods within a season switched nests for a second breeding attempt. Pairs often reused existing (old) nests constructed during previous years, and pairs that settled in old nests for their first breeding attempt were the most likely to switch nests for a second breeding attempt. Contrary to previous studies, nest predation and nest ectoparasitism had no influence on whether or not pairs switched nests. Moreover, second breeding attempts overall had significantly more mites than first breeding attempts, but there was more variation in the change of mite intensities for those pairs that switched nests for a second breeding attempt compared to pairs that did not switch. Furthermore, pairs that switched from one old nest to another nest between breeding attempts decreased the time between first and second breeding attempts when compared to pairs that reused their first nest for a second breeding attempt. Because nest-switching led to greater fledging success for second breeding attempts compared to birds that reused their nests, our results suggest that switching between nests is an adaptive reproductive strategy for Barn Swallows.

Breeding in alpine environments poses significant challenges to birds, requiring specific adaptations for survival. The Sclater's monal (Lophophorus sclateri), a regionally threatened, typical alpine pheasant species, is restricted to high‐elevation habitat from the East Himalayas to the mountains of west Yunnan, China. Due to its low population density and the difficulty of accessing its habitats, the breeding ecology of this species is understudied. Therefore, we aimed to understand the breeding behavior, nest site use, and life‐history traits that allow this monal species to cope with the alpine environment. During our fieldwork from March to June 2015 and 2016 in the Gaoligong Mountains in western Yunnan, China, we found six cliff nesting sites ranging from 3535 m to 3892 m. Three sites were active, with one being used in both years, and the remaining three were inactive but had been used in prior years. The clutch size was 2.75 ± 0.5 (2 or 3 eggs; n = 4 nests at three nesting sites), and all 11 eggs were successfully hatched. The female solely performed incubation, spending 97.2% of its time in incubating with an average duration of 25.69 ± 13.79 h (n = 43 bouts across three females) per on‐bout which indicates the female bird invested more time than other pheasants. High incubation attendance by females highlights the importance of increased parental care in ensuring reproductive success. These findings highlight that the Sclater monal exhibits specific breeding behaviors and nesting strategies that reflect adaption to harsh environments. Additionally, our observations of intense male–male interactions and reuse of nesting sites suggest that suitable nesting sites are limited, which could significantly impact population dynamics. Together, these insights are crucial for conserving this regionally threatened pheasant. The study focused on the breeding ecology of the Sclater's monal in the alpine environment of western Yunnan, China. It found that the species has a low population density and restricted nesting sites, with intense male–male competition observed. Females invest significantly more time in incubation, likely to cope with harsh conditions. These findings highlight the importance of understanding avian reproduction ecology for the conservation of threatened species like the Sclater's monal.

In this study, we investigated the Eurasian eagle owl (Bubo bubo) breeding in lowland forests in the trans-border area between western Slovakia, eastern Austria, and southern Moravia. The research provides new information on the reuse of nests by eagle owls and presents initial insights into population density and trends of eagle owls in the March-Thaya floodplains. Our 19-year monitoring has shown that the eagle owl has become a widespread breeder over the study area, with an increasing population trend. A total of 151 breeding attempts by eagle owls have been identified, occupying 82 natural nests (originally built by at least nine species of birds) and 12 artificial nests. With an average of 6.2 active nests per 100 km2 and a maximum of 17 active nests found in 2021 (~10.6 pairs per 100 km2), our findings represent one of the highest eagle owl breeding densities found, especially in comparison with core populations nesting in the mountains (the Carpathians, north-eastern Alps and the Bohemian Massif). Regarding the dynamics of nest reuse, our results reveal that only a third of nests used by eagle owls were reused by other raptors or storks (Ciconia sp.). Almost 50% of the natural nests in which eagle owl bred, subsequently disintegrated after the owlets had fledged. Lastly, black stork (Ciconia nigra) nests re-used by eagle owls were twice as likely to have disintegrated after the owlets had fledged than nests built by other bird species. Our results suggest that black stork nests in the March and Thaya floodplain forests are most susceptible to destruction.

Black-chinned Hummingbirds (Archilochus alexandri) began nesting inside a hardware store near El Paso, Texas, in the spring of 2015. At least 12 nesting attempts occurred inside the store through 2020, and all but 1 of them fledged young (91.7% nesting success). Nests were followed closely in 2019 and 2020, when 7 nesting attempts produced 13 fledglings. One female raised 4 broods between mid-April and early September 2020; this female laid eggs for her second, third, and fourth attempts while young from each previous attempt were still in the nest. The high nesting success and productivity that we observed probably resulted from nesting indoors, where the 2 major causes of nest failure in this species, predation and extreme weather, were absent. Old nests remained intact for multiple years inside the store, which probably facilitated multiple brooding because females often reused old nests rather than built new ones for subsequent attempts.

Nest reuse is often observed in large- and medium-sized birds, including hole-nesters, while in smaller passerines building open-cup nests it is rarely recorded. In this note we report a case of multiple nest reuse, observed in a residential garden in Poland. The nest was located on the wall of a farm building partly overgrown by Boston Ivy at the height of 2.3 m. The nest was occupied eight times between 2007 and 2023 by three bird species: Grey and Pied Wagtails and Common Blackbirds. The nest was built by Grey Wagtails in 2007, but in 2009 it was reconstructed considerably by blackbirds. The Blackbird cup with mud lining survived until 2023 and contained all other nests. We suggest that the most plausible reason for multiple nest reuse was the high quality of this nest site. However, we also found that the nest was used during warm, dry springs but avoided when weather conditions at the beginning of the breeding season were adverse. We hypothesize that cold and wet springs – thought to be associated with high costs of reproduction – may have influenced birds’ decision not to reuse the nest. To our knowledge, this is the longest case of nest reuse reported for passerines building open-cup nests.

Nest site availability plays an important role in the ecology of the birds inhabiting intensive agricultural landscapes. The removal of trees and snags due to logging is one of the main threats and the cause of the observed decline in many birds living in an agricultural landscape. When nests are lost, nesting passerines typically rebuild them for a new clutch. Additionally, relocating nests after a brood loss is a prevalent strategy used to avoid predators and brood parasites. Such a strategy is common to the Red-backed Shrike, which builds successive nests for each brood. Interestingly, clutch replacement may occur in unusual forms. This study describe three cases of Song Thrush nests reused by Red-backed Shrikes during one breeding season. The time and energy-saving behaviour or possible deterrence of nest parasitism could explain why the nests have been reused. However, due to the limited observations as compared to the total number of nests, further research is necessary to clarify this phenomenon.

Nest reuse is a relatively uncommon practice among passerines, particularly among multiple species. In June 2016 we documented a Sage Thrasher (Oreoscoptes montanus) nest in the Upper Green River Basin, Wyoming, being reused by a Loggerhead Shrike (Lanius ludovicianus) pair within the same season. The shrikes made structural changes to the nest, including removing nearly all sticks supporting the nest's exterior. The repurposing of an open-cup nest by a Loggerhead Shrike within the same breeding season has never been documented, and interspecific nest reuse by passerines in general is rare. The pervasiveness of this behavior, however, is poorly understood because instances are likely underreported.

Artificial burrows are considered an important management and conservation tool for burrowing owls (Athene cunicularia). This species regularly adorns natural and artificial burrows withmammal dung and other materials, which remain between years so that previous use of a nest site is often obvious. Moreover, ectoparasites (fleas) potentially overwinter in accumulated material and infest subsequent occupants. How evidence of prior use affects burrowing owl nest-site decisions is not completely understood. We examined potential effects of the presence of old nest material on reuse of nests by burrowing owls in southwestern Idaho, USA, during 2004 and 2005. We manipulated artificial burrows that owls used for nesting in the prior year by; 1) removing material from the entrance, tunnel, and nesting chamber and replacing it with fresh soil; 2) microwaving old nest material to kill ectoparasites before returning it; or 3) removing and returning material without treatment to serve as a control. Relative to removal burrows, odds of burrowing owl reuse of ‘control’ and “microwave” burrows were 3.5 and 3.8 times greater, respectively. Removing ectoparasites by microwaving did not increase odds of reuse relative to control burrows, and fleas were present on nestlings in all 3 treatment groups. Presence of old material may help owls locate specific burrows when returning from migration ormay provide physiological and feeding benefits. Thus, cleaning by removal of nest material from previously used artificial burrows may be counterproductive if maximizing reuse of nest sites by burrowing owls is a management objective.