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Birds are under selective pressure to orient their nests in a direction that reduces the impact of climatic extremes and the risk of the nest being detected by predators. Woodpeckers (Picidae), despite raising young in tree cavities that are safer from predators, should orient the entrances of their nest cavities in a direction that results in a favorable cavity microclimate. Because Picid nest cavity orientation is not well-studied in the Pacific Northwest of North America, we measured nest cavity orientation of White-headed Dryobates albolarvatus, Hairy D. villosus, and Black-backed Picoides arcticus Woodpeckers, Northern Flicker Colaptes auratus, and Williamson's Sapsucker Sphyrapicus thyroideus within burned and unburned, dry conifer forests of the eastern Cascade Range in Washington, USA (N = 684). Each woodpecker species had a mean angle of nest cavity orientation in a northerly or easterly direction and ranged from 12.3° for the Northern Flicker to 117.6° for the Black-backed Woodpecker. Hairy Woodpeckers, Northern Flickers, and White-headed Woodpeckers showed strong evidence for nonrandom nest cavity orientation, and Northern Flickers showed particularly high dispersion with a multimodal distribution of cavity orientations. Although the mean and variance of cavity orientations did not differ substantially between woodpeckers, cavity orientation differed based on nest tree species. Woodpeckers may orient their nest cavities in an easterly direction so that cavities warm quicker in the morning, to avoid hot afternoon temperatures and prevailing west and north westerly winds, and because the majority of cavities were located in burned forest where shading from canopy cover is reduced.
Nesting is a prerequisite for breeding in a wide range of birds, and nest-sites become a key resource ultimately influencing individual fitness. In that context, reuse of nest-sites by breeding pairs has been observed in a variety of bird species. White-collared Swifts Streptoprocne zonaris constitute one example in which reuse of nest-sites from previous reproductive seasons has been reported. In this study we explored this behaviour in the main location of the species in Cuba, the natural area of Topes de Collantes (south-central Cuba), where breeding pairs occupy several natural rocky caves. We also studied nest-sites locations to identify determinants for reuse and followed nest content to quantify nesting success. During a three-year period of study, 82 nests were constructed in 67 nest-sites at three nesting colonies located at the area. Nest-sites were occupied in the four placement-location combinations at the caves: ceiling-hole, ceiling-ledge, wall-hole and wall-ledge, and were located at a height range of 0.90 to 9 m. A total of 31 nest-sites were reused at least once, which implies an incidence of nest-site reuse for the area of 46.3%. Nest-site reuse was related to characteristics of the nest-site location: reused nest-sites were less often observed at the ceiling-ledge combination as well as at the highest locations in the caves. Nesting success was measured as success in producing at least one fledgling, and was higher in reused (87.1%) than in not-reused (59.5%) nest-sites. These results confirm the existence of some benefits of nest-site reuse in the Cuban populations of the White-collared Swift, suggesting that the high quality breeding pairs might detect and select particular nest-sites to guarantee a successful breeding. This study also highlights that conservation of the caves and their natural characteristics at the natural area of Topes de Collantes is key for the Cuban populations of the species.
A large part of European forests is managed using modern forestry techniques, and it is interesting to explore the relationships between forest bird abundance and variables describing the forests from the perspective of forest managers. The aim of our study was to identify these relationships through nation-wide bird monitoring and forestry data in Czechia. After controlling for the effect of altitude, the forest characteristics that exhibited a significant effect on the abundance in the highest number of species are the proportion of conifers, growth phase and tree damage. In the next step, we performed a principal component analysis to reveal general patterns in those species-specific responses. The main gradient obtained was determined by altitude and discriminated species associated with lowland forests (e.g. Common Starling Sturnus vulgaris, Spotted Flycatcher Muscicapa striata) from those associated with highland forests (e.g. Red Crossbill Loxia curvirostra, Tree Pipit Anthus trivialis). This suggests an important role of altitudinal climate zones in shaping forest bird abundance. The second gradient showed a cluster of species with higher abundance in broad-leaved forests with higher stem density, more vegetation layers, and more damaged (e.g. Common Redstart Phoenicurus phoenicurus, European Pied Flycatcher Ficedula hypoleuca). At the opposite end were clustered species with higher abundance in more coniferous forests, lower stem density, fewer vegetation layers and less damaged (e.g. Eurasian Siskin Spinus spinus, Crested Tit Lophophanes cristatus). The second gradient can be explained by forestry practices applied in Czechia. Specifically, broad-leaved forests generally have a longer logging cycle compared to coniferous forests, resulting in generally older stands exhibiting more signs of damage and multiple vegetation layers, while coniferous forests predominantly maintain a single-vegetation layer structure. Bird association with growth phase was independent from altitude and other forest characteristics.
Wildfire recurrence is a threat to North African forest ecosystems. The objective of this study is to assess the impact of fire on the avifauna of Algerian cork oak forests and evaluate their resilience in a conservation perspective. We adopted both synchronic sampling (selection of sites supposed representative of successional stages) and diachronic sampling (sampling of the same sites repeated over time) of the avifauna of cork oak stands situated in a fire-prone area of NE Algeria. Using multivariate analyses, we measured the degree of fire alteration of these ecosystems, reconstituted a post-fire successional series, tracked the post-fire recovery, and analyzed the response of each bird species. The results show that the number of species decreases after fire and then increases until it reaches a plateau at around 20–30 years of age. The responses of bird species to fire are relatively similar to those north of the Mediterranean (France, Spain) with few exceptions, in particular because the relatively early sampling includes some late winterers. After the disappearance of the forest species (e.g. Regulus ignicapilla, and Coccothraustes coccothraustes) and the appearance of a few open-habitat species immediately after the fire (e.g. Galerida cristata, Oenanthe hispanica), the former recolonise and the composition of the avifauna stabilises after around twenty years after fire. Even subjected to repeated fires, these forests seem to have the ability to regenerate and recover their pre-fire avifauna and vegetation structure within about 30 years. Despite the apparent resilience shown by these cork forests in the short-term, we do not know the consequences on strictly forest birds of an increase in fire frequency resulting from an increased human pressure and climate change, and recommend protection of these ecosystems to ensure their sustainability.
Hops (mainly Humulus lupulus varieties) are a globally significant agricultural crop, known mainly for their use in the brewing industry. Hop plantations create unique habitats for birds, with structural poles potentially serving as nesting sites for cavity nesting birds. We surveyed 321 hop plantations (inspecting 100 random poles in each) during the 2023 breeding season in Bavaria, Germany, and examined structural poles for the presence of nesting birds. We found 219 breeding pairs of 11 cavity-nesting species. The most frequent nesting species were Common Starling Sturnus vulgaris, Tree Sparrow Passer montanus, and Great Tit Parus major. The most nesting cavities were found in wooden and concrete poles, while metal poles were largely avoided. Nesting sites in metal and concrete poles were often selected due to structural imperfections, whereas wooden poles contained mainly cavities excavated by woodpeckers. We advocate for the retention of wooden poles over concrete/metal poles, as they are crucial nesting sites for birds which are important in pest control in hop plantations. For modern hop plantations with non-wooden poles, we recommend the use of nest boxes which can compensate for the loss of nesting sites and support local breeding bird populations.
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