Timing of arrival at breeding grounds determines spatial patterns of productivity within the population of white stork (Ciconia ciconia)

Abstract

Early arrival at breeding grounds have important fitness consequences for migratory birds, both at individual and population level. The aim of this study was to investigate how the timing of arrival at the breeding territories affects the spatial patterns of reproductive success within a population of white storks (Ciconia ciconia). Data were gathered annually for ca. 200 pairs of storks breeding in central Poland between 1994 and 2011. Geostatistical analysis of data indicated that in years of delayed arrival of the population (measured by the first quartile arrival date), the reproductive output of storks was negatively autocorrelated, which indicated that there was a tendency for pairs of high breeding success to neighbour with pairs of low success. By contrast, in years when first storks returned in early dates to the breeding grounds, their reproductive success did not show any kind of spatial autocorrelation. These results suggest that delayed return of the first-arriving storks of the population may increase intensity of intra-specific competition to the level at which high-quality breeding pairs monopolize most of available resources at the expense of neighbouring lowquality pairs, which have lower reproductive success as a consequence. Such hypothesis was further supported with the analysis of nesting densities, showing that the latearriving breeding pairs incurred greater fitness costs (or derived lower fitness benefits) while breeding in high densities comparatively to the early-arriving conspecifics.

Shortening day length as a previously unrecognized selective pressure for early breeding in a bird with long parental care

“…All the nests were visited in July/August and the timing of fledging was assigned to one of three following periods: (1) before July 20; (2) between July 20 and 31; and (3) after August 01. The distribution of nests within the population was consistent with a random pattern, where the mean nearest neighbour distance was 1.24-1.47 km (Janiszewski et al 2014a). Dense colonylike aggregations were not recorded in the study area.…”

Non-adaptive territory selection by a bird with exceptionally long parental care

“…In many migratory species of birds, there is a phenotype-dependent competition for early arrival at breeding grounds ( Møller, 1994 ). High-quality individuals are usually able to prepare more quickly for spring migration, migrate at a higher speed, and consequently, arrive at breeding grounds earlier than poor-quality conspecifics ( Aebischer et al, 1996 ; Hotker, 2002 ; Elmberg et al, 2005 ; Janiszewski, Minias & Wojciechowski, 2014b ). As many territories are not yet occupied early in spring, first-arriving individuals are able to choose the most attractive sites and initiate breeding earlier, which may provide additional reproductive benefits.…”

Distribution and breeding of the White Stork (Ciconia ciconia) in North Macedonia in 2015 and 2016

“…Nesting on trees was nearly abandoned in 2015-2016 with only 0.6%, while nesting on hay bales and stacks was completely abandoned. The first White Stork census found that 37.2% of the nests were placed on trees and 7.52% on hay bales (Jovani & Tella 2004;Denac 2006;Hilgartner et al 2014;Eggers et al 2015) and distance to the main feeding areas (Hilgartner et al 2014;Djerdali et al 2016a) are known to affect the breeding parameters, as is the combination of the en-vironmental factors with colony size (Janiszewski et al 2014;Djerdali et al 2016b), sometimes resulting with density-dependent brood reduction (Zurell et al 2015). These factors might be behind the observed differences in the breeding parameters among some regions in North Macedonia in 2015, but clear correlation between breeding densities and breeding parameters is lacking (Tab.…”