How avian nest site selection responds to predation risk: testing an ‘adaptive peak hypothesis’

Abstract

Summary1. Nest predation limits avian fitness, so birds should favour nest sites that minimize predation risk. Nevertheless, preferred nest microhabitat features are often uncorrelated with apparent variation in predation rates. 2. This lack of congruence between theory-based expectation and empirical data may arise when birds already occupy 'adaptive peaks'. If birds nest exclusively in low-predation microhabitats, microhabitat and nest predation may no longer be correlated even though predation ultimately shaped microhabitat selection. 3. This 'adaptive peak hypothesis' was tested for a population of Yellow Warblers (Dendroica petechia) focusing on two nest microhabitat features: concealment and height. Experimental nests measured relative predation risk both within and outside the microhabitat range typically occupied by natural nests to examine whether nest site choices made by birds restricted our ability to detect microhabitat effects on predation. 4. Within the natural range (30-80% concealment, >75 cm height), microhabitat-predation relationships were weak and inconsistent, and similar for experimental and natural nests. Over an extended range, however, experimental predation rates were elevated in exposed sites (<30% concealed), indicating a concealment-related 'adaptive plateau'. 5. Clay egg bite data revealed a concealment effect on avian predators, and the abundance of one avian predator group correlated with nest concealment among years, suggesting these predators may cue birds to modulate nest concealment choices. 6. This study demonstrates how avian responses to predation pressure can obscure the adaptive significance of nest site selection, so predation influences may be more important than apparent from published data.

Éxito de anidación de Turdus grayi (Passeriformes: Turdidae) en el Centro Ecológico Recreativo “El Zapotal”, Chiapas, México.

“…La altura de construcción del nido ha sido considerada como una estrategia evolutiva ante los depredadores (Latif, Heath, & Rotenberry, 2012). En relación a la cobertura vegetal esta variable no intervino significativamente en el modelo a escala local, debido a que al medirla dejamos de lado la influencia y el efecto del tamaño de la copa del árbol donde T. grayi anidó, por lo que los porcentajes de cobertura altos con coeficientes de variación bajos, de manera tal que podría-mos haber cometido sesgo y sobreestimamos estos.…”

Spatial distribution of display sites of Grey Peacock-pheasant in relation to micro-habitat and predators during the breeding season

“…There is a higher population of potential predators at these sites than elsewhere in its habitat, but the Grey Peacock-pheasant is able to carry out its courtship at these selected sites as it is diurnal, whereas most of its predators are nocturnal. In subsequent stages, the species may use different tactics to avoid predators, such as using vegetation cover during the nesting and brood rearing phase (Kirol et al 2012;Latif et al 2012;Suwanrat et al 2014). When displaying at scrapes there might be a trade-off between successful mating and predator risk similar to that in male Lesser Prairie-chicken (Tympanuchus pallidicinctus), which selects open areas for leks to display for females in spring, but also suffer from peak mortality at the same time (Hagen et al 2005;Larsson et al 2013).…”

Monk parakeet nest-site selection of electric utility structures in Texas

“…Where a bird chooses to build its nest is an important decision for its reproductive success (Gill, 1990;Latif, Heath, & Rotenberry, 2012). Avian nest-site choice is often associated with structural stability (reducing destruction by inclement weather, human disturbance, etc.…”