The Wilson Journal of Ornithology 123 ( 3 ): 486 - 491 , 2011 
SPATIAL VARIATION IN CLUTCH SIZE AND EGG SIZE WITHIN A 
COLONY OF WHISKERED TERNS ( CHL1DON1AS HYBR1DA) 
PIOTR MINIAS. 1 ? KRZYSZTOF KACZMAREK, 2 
TOMASZ JANISZEWSKI. 1 AND ZBIGNIEW WOJCIECHOWSKI 1 
ABSTRACT.—Egg and clutch si/e of Whiskered Terns (Chlidonias liybrida) in relation to their location within the 
colony were investigated at Jeziorsko Reservoir, central Poland. All nests <n = 125) in the colony were individually marked 
and mapped using a Global Positioning System. Four nest clusters were distinguished within the colony based on the patchy 
distribution of floating vegetation which delineated potential nesting areas. Early breeding Whiskered Terns nested in more 
central and denser parts of nest clusters and late breeders nested in more peripheral zones of the clusters (trend analysis: 
F — 20.47, df = I, P < 0.001). Pairs which nested closer to the centers of clusters had larger clutch sizes (trend analysis: 
^ ~ -’-70. df — I, P — 0.019), hut there was no relationship between clutch size and distance to the colony center 
(F ~ df - 2, P = 0.69). Edge clutches had higher coefficient of variation in egg volume in comparison to more 
central clutches (trend analysis: F = 5.07. df - I, P = 0.028). Tents nesting in intermediate densities laid eggs of die 
highest length and volume (trend analysis: F = 7.17. df = I. P 0.009; F = 6.35, df = 1, P = 0.014. respectivelyi. We 
suggest that establishment of particular nest clusters in the Whiskered Terns colony at Jeziorsko Reservoir followed a 
central-periphery model. Received 8 October 2010, Accepted I February 20/1. 
Breeding individuals of different quality ex¬ 
pressed by age, experience or physical condition 
may not be evenly distributed across colonies of 
waterbirds (Coulson 1968a). Nesting sites within 
a colony usually differ in attractiveness and 
intense competition may occur between pairs for 
favored sites (Birkhead and Furness 1985). 
Distribution of breeding pairs within the colony 
and nesting in higher densities should provide 
more efficient protection against predators and 
promote higher breeding success (Velando and 
Freire 2001). Several studies have demonstrated 
reduced egg/chick losses in the center of water- 
bird colonies (Gotmark and Andersson 1984, Oro 
1996, Yorio and Quintana 1997). Individuals of 
higher quality should dominate weaker conspe- 
cifics and relegate them to peripheral zones; thus, 
they are expected to occupy the most favorable 
sites in colonies (Porter 1990). However, not all 
species of waterbirds follow the central-periphery 
model of nest distribution. A central-satellite 
model was developed to explain spatial patterns 
characteristic for colonial waterbirds breeding in 
heterogeneous habitats (Velando and Freire 
2001). This model assumes low-quality pairs nest 
around the most favorable sites occupied by high- 
quality pairs to achieve extra-pair copulations or 
Department of Teacher Training and Biodiversity 
Studies. University of Lridz. Banacha 1/3, 90-237 LodJ. 
Poland. 
Df s,erli "S“ I' 3 . ’M25 
3 Corresponding author; e-mail: pminias@op.pl 
acquire a better site or mate in succeeding years. 
The central-satellite model of nest distribution has 
been reported for European Shag (Phalacrocorax 
aristoloh'Hs) (Velando and Freire 2001). Pelagic 
Cormorant (P, pelagicus ) (Siegel-Causey and 
Hunt 1986), and Blue-fooled Booby (Sula nc- 
bouxii) (Nelson 1978). 
Spatial variation in breeding success and chick 
survival rates has been described for several 
colonial waterbirds (e.g., Coulson 1968a, Dexhei- 
mer and Southern 1974). but studies of egg and 
clutch size are lacking. High repeatability and 
heritahility of egg size in comparison to other 
reproductive characteristics such as laying date 
suggests its considerable adaptative significance 
(Lessens et al. 1989). Egg size of several larid 
species exerted a profound impact on offspring 
performance and survival rates (Davis 1975. 
Thomas 1983, Bolton 1991). Egg size has also 
been Found to increase with age and breeding 
experience of females (Nisbet et al. 1984, Syde- 
man and Emslie 1992) and has been correlated 
with morphological indices of maternal quality, 
including size or mass (Bolton et al. 1993). Clutch 
size is also known to be affected by condition of 
females (Rowe et al. 1994), which has been 
confirmed in larids (Coulson and Porter 1984). 
Both clutch size and egg size have been suggested 
as proxies of parental quality (Amundsen and 
Stokland 1990, Slagsvold and Lifjeld 1990) and 
their spatial variation within the colony is 
assumed to reflect distribution of different-quality 
breeding pairs. 
The Whiskered Tern (Chlidonias hybrida) is a 
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