Influence of Moisture and Food Supply on the Movement Dynamics of a Nonbreeding Migratory Bird (Parkesia noveboracensis) in a Seasonal Landscape

Abstract

We radiotracked Northern Waterthrushes (Parkesia noveboracensis) in four habitats in Puerto Rico during two winters (i.e., January-April) in 2003 and 2004 to determine the ecological determinants of diurnal space use and overwinter sitepersistence in this species. The majority of birds (69%) were sedentary and used a contiguous area within a single habitat over the winter period. A smaller percentage (31%) initially used a contiguous area within a single habitat but then permanently moved from that area to another disjunct location (mean = 418 m). Most of these movements were out ofthe two habitats (dry forest and Black Mangrove) that became the driest from January to mid-March and into wetter mangrove areas. The primary determinants of movement probability were moisture and food availability on each bird's home range. Foraging areas of birds that eventually moved were drier and had lower food availability than areas used by site-persistent individuals. The sites that these itinerant birds moved to were wetter and had higher food availability, which suggests that individuals moved in response to changing resources. Our results (1) indicate that habitats used by this species differ in suitability and (2) support previous findings that turnover rates within a habitat could serve as an indicator of habitat quality. The ability to predict behavioral responses of individuals to habitat conditions that vary across space and time is essential for understanding individual and population responses to habitat loss and the effects ofa changing climate in the New World tropics. Influencia de la Humedad y del Suministro de Alimentos sobre las Dinámicas de Movimiento de un Ave Migratoria No Reproductiva {Parkesia noveboracensis) en un Paisaje EstacionalRESUMEN.-Seguimos mediante transmisores de radio a individuos de Parkesia noveboracensis en cuatro ambientes en Puerto Rico durante dos inviernos (i.e., enero-abril) en 2003 y 2004 para establecer los determinantes ecológicos del uso del espacio diurno y la persistencia en sitios de invernada en esta especie. La mayoría de las aves (69%) fueron sedentarias y usaron un área contigua dentro de un único ambiente a lo largo del período invernal. Un porcentaje más pequeño (31%) usó inicialmente un área contigua dentro de un único ambiente pero luego se movió de modo permanente desde esta área a otro sitio disyunto (media = 418 m). La mayoría de estos movimientos fueron hacia afuera de los dos ambientes (bosque seco y manglar negro) que se tornaron los más secos desde enero hasta mediados de marzo y hacia áreas de manglar más húmedas. Los determinantes primarios de la probabilidad de movimiento fueron la humedad y la disponibilidad de alimento en el ámbito de hogar de cada ave. Las áreas de forrajeo de las aves que eventualmente se movieron fueron más secas y tuvieron menor disponibilidad de alimentos que las áreas usadas por individuos que persistieron en los sitios. Los sitios a los que estas aves itinerantes se movieron fueron más húmedos y tuvieron mayor disponibilidad de alimento...

Sex and Age Differences in Site Fidelity, Food Resource Tracking, and Body Condition of Wintering Kirtland's Warblers (Setophaga Kirtlandii) in the Bahamas

“…The marked emigrants we relocated at other study sites after site shifts within a winter were found to have moved from sites with low food resources to sites with higher food resources (i.e., significant for ripe fruit, marginally significant for ground arthropods), as expected for birds tracking ephemeral food resources (Sherry and Holmes 1996). These site shifts in response to food-resource declines are similar to the itinerant movements of Northern Waterthrushes (Parkesia noveboracensis) as they track changes in food resources at different sites associated with differential changes in moisture as the winter becomes drier (Smith et al 2010(Smith et al , 2011a. Although the moisture gradients among habitat patches used by warblers on Eleuthera are not as steep as the gradients encountered by wintering Northern Waterthrushes (i.e., dry forest to mangroves) and fruiting phenology may be out of phase with moisture availability (e.g., fruiting phase terminates as rainfall arrives), the itinerant patterns of response to habitat change in a heterogeneous landscape appear to be similar in the two species.…”

“…Experience, perhaps due to familiarity with a food source or shrub species and their locations, may enable adults to obtain asynchronously produced fruit shortly upon ripening more consistently than juveniles, while reducing the standing crop available to less experienced birds. In addition, familiarity with locations of widely scattered rich food patches obtained in the previous winter(s) may also give experienced birds an advantage (Smith et al 2011a), especially in late winter of dry years. Consistent with this scenario was an instance in which an individual (OO-XO) used the same disjunct site each winter (DD site in early winter and midwinter, and then shifted 5.1 km to the GF site in late winter in both 2005-2006 and 2006-2007), which suggests year-to-year stability of movement patterns, at least while resources varied consistently within winters.…”

Habitat‐dependent occupancy and movement in a migrant songbird highlights the importance of mangroves and forested lagoons in Panama and Colombia

“…This is likely because mangroves and cienagas retain more moisture while soils and vegetation in secondary forests and freshwater wetlands dry out, leaving fewer resources (i.e., phytophagous and aquatic emergent arthropods) for birds occupying those habitats (Smith et al, 2011). This is likely because mangroves and cienagas retain more moisture while soils and vegetation in secondary forests and freshwater wetlands dry out, leaving fewer resources (i.e., phytophagous and aquatic emergent arthropods) for birds occupying those habitats (Smith et al, 2011).…”

“…Many species of migratory birds occupy mangrove and lowland riparian tropical forests during the overwintering period, as they tend to have higher prey abundance than drier habitats (e.g., Chan, Yu, Zhang, & Dudgeon, 2008;Smith, Reitsma, & Marra, 2011;Wunderle, Lebow, White, Currie, & Ewert, 2014). Conservation of migratory species is challenging because their shifting distributions make it difficult to identify the potentially diverse factors limiting populations at different points throughout the annual cycle (Marra, Cohen, Loss, Rutter, & Tonra, 2015;Runge, Martin, Possingham, Willis, & Fuller, 2014;Webster, Marra, Haig, Bensch, & Holmes, 2002).…”

“…Density can be a cue for resource availability (Stamps, 1991) and nonterritorial birds are more likely to move out of (i.e., not persist in) habitats that decline in quality over time compared to species that have invested time in establishing a territory. Despite our understanding of the occurrence of withinseason movements of overwintering birds, few studies have examined habitat-related factors that may be driving these intra-seasonal movements (but see Smith et al, 2011;Wunderle et al, 2014). Recent evidence of large-scale intra-tropical migration has also been observed in some species that are thought to avoid competition or track resources to increase their chances for survival (Koleček et al, 2018;Stutchbury et al, 2016).…”