Individual responses in spring arrival date to ecological conditions during winter and migration in a migratory bird

Abstract

Summary 1.We studied lifetime arrival patterns in the barn swallow (Hirundo rustica L.) in relation to variation in ecological conditions, as reflected by the normalized difference vegetation index (NDVI) in the Sub-Saharan winter quarters and at stopover sites in North Africa. 2. Migratory birds have recently advanced their arrival dates, but the relative role of microevolution and phenotypic plasticity as mechanisms of response to changing environmental conditions remains unknown. To distinguish between these two possibilities, we investigated the change in the arrival date using cross-sectional and longitudinal analyses. 3. We predicted that the effect (i.e. slopes) of environmental conditions in stopover or winter areas on arrival date should be similar using cross-sectional and longitudinal analyses in case phenotypic plasticity is the underlying mechanism, or they should differ in case microevolution is the mechanism. 4. As expected according to a previous cross-sectional study, we found an advance in the arrival date when ecological conditions improve in stopover areas and a delay in the arrival date when ecological conditions improve in the winter quarters. 5. Change in the arrival time at the breeding grounds due to ecological conditions found en route and, in the winter areas, was mainly due to phenotypic plasticity as shown by similarities in the slopes found in these relationships using cross-sectional and longitudinal analyses. 6. We also investigated sex and age of barns swallows as sources of variation in the arrival time with respect to conditions experienced in winter and stopover areas. We found that earlier arrival at the breeding grounds due to prevailing ecological conditions found en route in North Africa was similar for males and females of all age-classes. In contrast, individuals tended to delay departure when ecological conditions improved in the winter quarters, but this delay differed among age classes, with old individuals delaying departure more than middle-aged and yearling birds. 7. The migratory response of individuals to changing climatic conditions experienced during different parts of their life provides evidence for individuals responding differently to prevailing conditions in the winter quarters depending on their age, but not to conditions experienced en route during spring migration.

Social cues are preferred over resource cues for breeding-site selection in Barn Swallows

“…Two types of direct resource cues (i.e., nestsite characteristics related to predation and potential foraging habitats), two types of indirect social cues (i.e., the number of breeding pairs and breeding success in the previous year), number of undamaged old nests, number of old nests, and individual age were used as the explanatory variables. Since the arrival dates were suggested to differ with age in European Barn Swallows (Balbontin et al 2009), ages of males that arrive first at the nest sites were used. The considered spatial scales were the nest-site and home-range.…”

Rainfall-induced changes in food availability modify the spring departure programme of a migratory bird

“…Two recent studies suggest that tropical precipitation may vary enough to influence the timing of spring arrival. Individual barn swallows (Hirundo rustica) arrived earlier at breeding sites in years when the normalized difference vegetation index (NDVI) was high on non-breeding grounds in western Africa and at staging areas north of the Sahara desert [11,19]. Because positive NDVI values signal elevated primary productivity, these studies reasoned that increased food resources owing to high rainfall helped birds depart earlier from non-breeding or staging sites and arrive sooner at breeding grounds.…”

Identification of Putative Wintering Areas and Ecological Determinants of Population Dynamics of Common House-Martin (Delichon urbicum) and Common Swift (Apus apus) Breeding in Northern Italy

“…Despite the large degree of uncertainty in the results and the call for validation through independent methods (e.g., ring recoveries), the approach of Szép and Møller (2005) and Szép et al (2006) is the only one applicable to species whose ecological characteristics have prevented the collection of large datasets of ring recoveries by common fields methods. As an index of environmental conditions, Szép and Møller (2005) and Szép et al (2006) used the Normalized Difference Vegetation Index (NDVI), a general index of primary productivity that, in turn, determines secondary productivity in general and availability of flying insects in particular and, therefore, may affect winter mortality and population size of aerial insectivores (Saino et al 2004, Szép et al 2006, Giralt and Valera 2007, Balbontin et al 2009). In addition, values for this index are readily available for wide regions of Africa.…”