The Adaptive Significance of Colonial Breeding in the Grey Heron Ardea cinerea: Inter- and Intra-Colony Variability in Breeding Success

Abstract

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Factors affecting the length of the breeding cycle and the frequency of nest attendance by Grey HeronsArdea cinerea

“…The number of chicks fledged may increase and the duration of the nestling period decrease when more food is provided (Lack 1968). Although clutch size and hatching success were similar at several Belgian heronries, the average number of chicks fledged per pair varied considerably between colonies, perhaps because of differences in the rate at which food is delivered to the nest (van Vessem & Draulans 1986).…”

Colony Development and Density-Dependent Processes in Breeding Grey Herons

“…A similar decline in the number of fledglings with a later date of the onset of breeding was observed for Grey Herons in Poland, although it was not observed every year [19]. Brood size is often larger in earlier breeders within a reproductive season in birds [47], as observed in Grey Herons [7,48,49] and other heron and egret species [50][51][52]. On the other hand, mean brood size increases with the age of parents [53,54].…”

“…Instead of tracking yearly changes in a single colony, intercolonial comparisons in the same year are useful to detect densitydependent processes, and such comparisons have been conducted in herons and egrets. Results have shown that final breeding success is negatively correlated with colony size in Grey Herons (Ardea cinerea) in Belgium [7] and Great Blue Herons (Ardea herodias) in Canada [8]. However, in Grey Herons in northern Poland, breeding success increases with colony size [9].…”

Distribution and Foraging Behaviour of Grey Herons Ardea cinerea in Adjacent Tidal and Non-Tidal Areas

“…Large herons (Ardeidae), such as the Grey Heron Ardea cinerea and the related Great Blue Heron A. herodias, breed either solitarily or in colonies of varying size (e.g., Cramp and Simmons 1977, Krebs 1978, Hancock and Kushlan 1984, van Vessem and Draulans 1986, and have been reported both to defend feeding territories and to forage in flocks (e.g., Lack 1968, Ward and Zahavi 1973, Krebs 1974, Cook 1978, van Vessem et al 1984, Dowd and Flake 1985, van Vessem and Draulans 1987a. This variability has been related to differences in the predictability of food resources; rivers and fish ponds, for example, have been considered to provide spatially and temporally more predictable feeding conditions than tidal and drying-out swamp conditions (Ward and Zahavi 1973, Krebs 1978, van Vessem et al 1984.…”