Food Limitation During Breeding in a Heterogeneous Landscape

Abstract

Breeding success in birds may be determined by the availability of food that parents can provide to growing nestlings. A standard method for testing the occurrence of food limitation is to provide supplemental food during different parts of the breeding period. If there is spatial variation in the strength of food limitation, the effect of such an experiment should also vary spatially. We investigated whether the strength of food limitation during nestling rearing in the European Starling (Sturnus vulgaris) was related to the management intensity of agricultural landscapes. We fed birds mealworms during the nestling period in landscapes with high or low local availability of pasture, the preferred foraging habitat. Both habitat and food supplementation affected growth and survival of nestlings; the effects of the food-supplementation experiment were generally stronger than those of habitat. Mortality mainly struck the last-hatched chick. Both habitat and food supplementation positively affected nestling growth, measured as nestling tarsus length. In addition, food supplementation positively affected feather growth and asymptotic mass. Contrary to expectation, no interactions existed between effects of habitat and food supplementation, which suggests that breeding success was limited by food availability in both landscapes. Potential reasons for this lack of effect are parental compensation and low statistical power. Also, breeding densities were higher in landscapes with more pastures, possibly equalizing the per-capita availability of food. Thus, our results demonstrate that reproductive success was limited by availability of food when local availability of preferred foraging habitat was either low or high, but fail to demonstrate spatial variation in the strength of food limitation. Escasez de Alimentos durante el Período Reproductivo en un Paisaje Heterogéneo

Food Regulates Reproduction Differently in Different Habitats: Experimental Evidence in the Goshawk

“…Prior to this study, however, local ecological conditions have been largely overlooked in food supplementation studies performed in the wild. Furthermore, in the few studies in which the idea that small‐scale differences in food availability might influence experimental effects has been considered (Gonzáles et al 2006, Granbom and Smith 2006), local landscape composition and/or information on multiple‐species prey diversity were not quantified. This is unfortunate, because to be able to definitively conclude that experimental food supplementation contributes differently to reproductive performance between habitats, detailed measurements of territory‐specific food levels are required.…”

“…For example, breeding performance may be more constrained by food in low-quality habitats, but it may be less limited by food in highquality habitats (Hakkarainen et al 2003, Lo˜hmus 2003). Yet, differences in habitat quality have seldom been controlled for in food supplementation studies performed in the wild (but see Gonza´les et al 2006, Granbom andSmith 2006), and no such studies, to our knowledge, have outlined detailed information on accompanying habitat-specific natural food levels. Similarly, even though food supplementation experiments commonly have been used (Martin 1987, Magrath 1990 to reveal details about the trade-off between offspring quantity and quality Fretwell 1974, Winkler andWallin 1987), we are aware of no studies that have tested whether extra food affects the quantity-quality trade-off differently in post-hatching situations when natural food levels differ between habitats.…”

The role of food, weather and climate in limiting the abundance of animals

“…It also illustrated the importance of using the correct food, and at the right point in the life cycle when undertaking supplemental feeding experiments. When Granbom & Smith (2006) fed starlings with mealworms during the nestling period the survival and growth rate of nestlings increased. Their breeding success and density was limited by the availability of protein food for their young.…”

Effects of Native and Non‐Native Grassland Plant Communities on Breeding Passerine Birds: Implications for Restoration of Northwest Bunchgrass Prairie

“…Shifts in plant communities from native to non-native plants may affect nest predation levels by altering nest site quantity and quality (e.g., degree of concealment or predator access) and/or nest predator activity (e.g., density or behavior). Food availability also limits reproductive success of birds, typically by delaying or aborting nest initiation (Ortega et al 2006), increasing starvation rates by reduced food abundance or foraging substrates (Maron & Lill 2005;Granbom & Smith 2006), and/or increasing predation risk from increased begging and/or reduced attentiveness of foraging adults (Dewey & Kennedy 2001;Zanette et al 2003). Several studies comparing native grasslands versus those dominated by non-native vegetation suggest that food limitation may be an important mechanism in reducing grassland bird populations (Bock et al 1986;Flanders et al 2006; but see Jonas et al 2002).…”