Demographic Responses by Birds to Forest Fragmentation

Abstract

Despite intensive recent research on the effects of habitat loss and fragmentation on bird populations, our understanding of underlying demographic causes of population declines is limited. We reviewed avian demography in relation to habitat fragmentation. Then, through a meta-analysis, we compared specific demographic responses by forest birds to habitat fragmentation, providing a general perspective of factors that make some species and populations more vulnerable to fragmentation than others. We obtained data from the scientific literature on dispersal, survival, fecundity, and nesting success of birds. Birds were divided into subgroups on the basis of region, nest site, biogeographical history, and migration strategy. Species most sensitive to fragmentation were ground-or open-nesters nesting in shrubs or trees. Residents were equally sensitive to fragmentation in the Nearctic and Palearctic regions, but Nearctic migrants were more sensitive than Palearctic migrants. Old World species were less sensitive than New World species, which was predicted based on the history of forest fragmentation on these two continents. Pairing success was the variable most associated with fragmentation, suggesting an important role of dispersal. Fledgling number or condition, timing of nesting, and clutch size were not associated with sensitivity to fragmentation, suggesting that negative fragmentation effects on birds do not generally result from diminished food resources with increasing level of fragmentation. Future studies on demographic responses of birds to habitat fragmentation would be more effective if based on a combination of measures that can distinguish among the demographic mechanisms underlying population changes related to habitat fragmentation.Key Words: bird demography, edge effects patch size, habitat loss, meta-analysis, patch isolation Respuestas Demográficas de Aves a la Fragmentación de BosquesResumen: A pesar de la reciente investigación intensiva sobre los efectos de la pérdida y fragmentación del hábitat sobre poblaciones de aves, nuestro entendimiento de las causas demográficas subyacentes en laa declinaciones poblacionales es limitado. Revisamos la demografía aviar en relación con la fragmentación del hábitat. Posteriormente, mediante un meta análisis comparamos las respuestas demográficas específicas de aves de bosque a la fragmentación del hábitat, lo que proporcionó una perspectiva general de los factores que hacen que algunas especies y poblaciones sean más vulnerables a la fragmentación que otras. Obtuvimos datos de la literatura científica sobre dispersión, fecundidad yéxito de anidación de aves. Las aves fueron divididas en subgrupos con base en la región, sitio de anidación, historia biogeográfica y estrategia de migración. Las especies más sensibles a la fragmentación anidaban sobre el suelo oáreas abiertas en matorrales oárboles. Las especies residentes fueron iguamente sensibles a la fragmentacíón en las regiones Neártica y Paleártica, pero los migrantes Neárticos fueron más sensibles que l...

Survival of Adult Songbirds in Boreal Forest Landscapes Fragmented by Clearcuts and Natural Openings

“…These patterns hold true regardless of migratory strategy, affinity for clearcut habitat, or the proportion of transients in the population ( Fig. 2; see also Lampila et al 2005). However 2 of 14 species we studied did experience lower apparent survival in landscapes altered by clearcutting, and for several others there was some suggestion of reduced apparent survival.…”

“…Thus matrix habitat influenced demographic parameters and likely affected habitat quality in fragments, but effects on incidence were less pronounced (Bayne and Hobson 2002a). As this demonstrates, knowledge of demographic responses affords a more complete understanding of the resilience of bird populations to landscape-scale habitat management, facilitating development of sound conservation guidelines (Sallabanks et al 2001, Bayne and Hobson 2002b, Donovan et al 2002, Lampila et al 2005). …”

“…Research has documented local numerical changes to land bird populations resulting from boreal forest management activities (e.g., Niemi et al 1998, Whitaker and Montevecchi 1999, Imbeau et al 2000. However, demographic responses are harder to measure, and at present little information is available linking changes in the distribution and abundance of boreal birds to demographic and population processes (Downes et al 2000, Rich et al 2004, Anders and Marshall 2005, Lampila et al 2005.…”

“…We realize that peatlands and clearcuts differ in many ways, particularly vegetation and site productivity, but given the importance of movement in demographic studies we felt it was important to compare landscapes that were composed of structurally analogous matrices of open and forested habitats. Interspecific comparisons of demographic responses to habitat change can improve our understanding of avian life history strategies and the manner in which different species respond to and compensate for environmental change (Martin 1995, Lampila et al 2005), so we expanded our analyses to include tests for patterns across species.…”

Matrix mediates avian movements in tropical forested landscapes: Inference from experimental translocations

“…05.025 are disproportionately declining in fragmented forests worldwide, with Neotropical-Nearctic migrants (e.g., Askins et al, 1990;Robbins et al, 1989) and Neotropical residents (e.g., Sigel et al, 2006;Sodhi et al, 2004;Stouffer et al, 2009) particularly impacted. Dispersal limitation is increasingly identified as a dominant mechanism underlying their demise (Lampila et al, 2005;Stratford and Robinson, 2005). We experimentally translocated 142 birds from their territories across three landscape treatments: landscapes fragmented by residential (peri-urban) development (i.e., peri-urban matrix), landscapes fragmented by bauxite mining (i.e., bauxite matrix), and landscapes comprising continuous forest (i.e., natural ''matrix'').…”