TIMING AND SPACING OF BROODS IN THE BLACK‐HEADED GULL LARUS RIDIBUNDUS

Abstract

SUMMARY The nests of the Black‐headed Gull Larus ridibundus are closely aggregated into dense colonies and their use synchronized, these two phenomena together tending to produce a maximal clumping effect. Within such a colony however, nests were found to be spaced out to produce a non‐random uniform distribution. The commonest distance between neighbouring nests was found to be about one metre, in contrast to related species. This study was concerned with two aspects of this distribution pattern; its survival value and its behavioural causation. It was found that pairs nesting just outside the colony had a much lower breeding success than those nesting in the colony and that nests on the colony fringe had a slightly lower success than those in the centre. Pairs laying during the peak laying period had a higher breeding success than pairs laying either earlier or later in the season. Since by far the most important mortality agent was predation, it seems likely that both clustering and synchronization of nesting function as antipredator systems and arguments in favour of this are discussed. Variations in nest‐spacing within the colony were not correlated with variations in breeding success. In the causation of the spacing between nests, territorial aggression was demonstrated to be an effective dispersion mechanism and the way in which this mechanism works was investigated in detail. This spacing mechanism was not sufficient by itself to explain the observed densities, which were higher than one would expect from the aggression alone; there was also some tendency for birds establishing a new nest‐site to cluster close to others. The interaction between this, the territorial aggression of the residents and the subsequent avoidance responses of the settling birds, can explain the nest spacing pattern and probably also the observed densities.

Identifying Environmental Determinants of Diurnal Distribution in Marine Birds and Mammals

“…The result is consistent with a pier-marina-beach-elsewhere model (n = 3) presented by Damania et al (2005), in which flows from all three loafing habitats into the elsewhere category were driven primarily by a low tide. It is also consistent with other studies that suggest gulls leave loafing habitats at low tide, probably as a result of increased food availability (Patterson, 1965;Drent, 1967;Delius, 1970;Galusha and Amlaner, 1978;Wondolowski, 2002).…”

Is it always beneficial to breed in the centre? Trade-offs in nest site selection within the colony of a tree-nesting waterbird

“…Further research on this species revealed that its population size is limited by the availability of nesting sites in the colony centre (Porter and Coulson 1987), and that centrally nesting individuals have higher survival rates (Aebischer and Coulson 1990). Central-periphery gradients of reproductive success were also confirmed in the Black-headed Gull Chroicocephalus ridibundus (Patterson 1965), Ring-billed Gull Larus delawarensis (Dexheimer and Southern 1974) and Caspian Tern Hydroprogne caspia (Antolos et al 2006). Higher chick survival in the centres of colonies has also been found in the Common Tern Sterna hirundo (Becker 1995) and Herring Gull Larus argentatus (Savoca et al 2011).…”

Linking anti-predator behaviour and habitat quality: group effect in nest defence of a passerine bird

“…Studies have shown that, outside the breeding season, reducing the area of a high-quality patch significantly reduces the size of heterospecific foraging groups (Beauchamp 2008;Siffczyk et al 2003), which decreases the probability of an approaching predator being detected (Beauchamp 2008;Griesser 2009). During the reproductive season, breeding success may increase with the number of close neighbours including heterospecifics (Alatalo and Lundberg 1984;Berg et al 1992;Fuchs 1977;Haas 1985;Johnsson 1994;Patterson 1965;Wiklund and Andersson 1994), which, in turn, is higher in high-quality habitats. In some bird species, there is a strong association between egg and nestling survival in groups as opposed to nesting alone (Götmark and Andersson 1984).…”