Factors affecting breeding season survival of red-headed woodpeckers in South Carolina

Juvenile survival of a burned forest specialist in response to variation in fire characteristics

Pyrodiversity, defined as variation in fire history and characteristics, has been shown to catalyse post-fire biodiversity in a variety of systems. However, the demographic and behavioural mechanisms driving the responses of individual species to pyrodiversity remain largely unexplored. We used a model post-fire specialist, the black-backed woodpecker (Picoides arcticus), to examine the relationship between fire characteristics and juvenile survival while controlling for confounding factors. We radio-tracked fledgling black-backed woodpeckers in burned forests of California and Washington, USA, and derived information on habitat characteristics using ground surveys and satellite data. We used hierarchical Bayesian mixed-effects models to determine the factors that influence both fledgling and annual juvenile survival, and we tested for effects of fledgling age on movement rates. Burn severity strongly affected fledgling survival, with lower survival in patches created by high-severity fire compared to patches burned at medium to low severity or left unburned. Time since leaving the nest was also a strong predictor of fledgling survival, annual juvenile survival and fledgling movement rates. Our results support the role of habitat complementation in generating species-specific benefits from variation in spatial fire characteristics-one axis of pyrodiversity-and highlight the importance of this variation under shifting fire regimes. High-severity fire provides foraging and nesting sites that support the needs of adult black-backed woodpeckers, but fledgling survival is greater in areas burned at lower severity. By linking breeding and foraging habitat with neighbouring areas of reduced predation risk, pyrodiversity may enhance the survival and persistence of animals that thrive in post-fire habitat.

Variation in individual autumn migration and winter paths of Great Lakes red-headed woodpeckers (Melanerpes erythrocephalus)

Migratory movements of facultative migrants are poorly understood due to their irregular and often unpredictable occurrence. However, tracking such movements is important for understanding population dynamics, informing annual cycle conservation plans, and identifying possible cues of facultative migration. We used pinpoint GPS tags to track autumn and winter movements of migratory red-headed woodpeckers (Melanerpes erythrocephalus) to better understand migration frequency, timing, and routes for birds breeding in managed oak savanna systems in the North American Great Lakes region. Proportions of individuals migrating differed between the two sites, with 72% of the Ohio population migrating, while no individuals in the Minnesota population migrated. Of the Ohio birds that migrated, their movements were highly variable in distance and direction but generally occurred south of the breeding site. Wintering sites ranged from 111 – 218 km from the breeding site. Cover types occupied during migration and wintering were almost exclusively small patches of closed-canopy hardwood forest within agricultural matrices. We documented one-time movements in migratory and non-migratory individuals during the year that have not previously been described in facultative migrants. We found no evidence of a harness or marker effect on proportions of individuals migrating, migration return rates, or annual survival regardless of migration.

Urbanization level and woodland size are major drivers of woodpecker species richness and abundance

Urbanization is a process globally responsible for loss of biodiversity and for biological homogenization. Urbanization may have a direct negative impact on species behaviour and indirect effects on species populations through alterations of their habitats, for example patch size and habitat quality. Woodpeckers are species potentially susceptible to urbanization. These birds are mostly forest specialists and the development of urban areas in former forests may be an important factor influencing their richness and abundance, but documented examples are rare. In this study we investigated how woodpeckers responded to changes in forest habitats as a consequence of urbanization, namely size and isolation of habitat patches, and other within-patch characteristics. We selected 42 woodland patches in a gradient from a semi-natural rural landscape to the city centre of Poznań (Western Poland) in spring 2010. Both species richness and abundance of woodpeckers correlated positively to woodland patch area and negatively to increasing urbanization. Abundance of woodpeckers was also positively correlated with shrub cover and percentage of deciduous tree species. Furthermore, species richness and abundance of woodpeckers were highest at moderate values of canopy openness. Ordination analyses confirmed that urbanization level and woodland patch area were variables contributing most to species abundance in the woodpecker community. Similar results were obtained in presence-absence models for particular species. Thus, to sustain woodpecker species within cities it is important to keep woodland patches large, multi-layered and rich in deciduous tree species.