The breeding biology of Western and Semipalmated Sandpipers was studied for four years near Nome, Alaska. Despite a short breeding season and a putatively invariant clutch size, there were seasonal declines in the fecundity of both sandpiper species. Most females produced only one clutch ( > 98%), but often laid fewer than four eggs (7.6-34.5% of first nests). Clutches of 2-3 eggs were initiate...

Although the possibility that food and predators may interact in limiting avian populations has long been recognized, there have been few attempts to test this experimentally in the field. We conducted a manipulative food addition experiment on the demography of Song Sparrows (Melospiza melodia) across sites that varied in predator abundance, near Victoria, British Columbia, Canada, over three ...

Few studies have examined how avian life-history traits vary within populations as elevation increases and climate becomes more severe. We compared egg and clutch sizes of Mountain Bluebirds (Sialia currucoides) nesting at two elevations (1500 m and 2500 m above sea level) in the Bighorn Mountains of Wyoming over two years. Eggs laid by females at the high-elevation site were, on average, signi...

Dolenec, Z.: Some breeding traits of the pied wagtail (Motacilla alba) in NW Croatia. Nat. Croat., Vol. 20, No. 1., 209–214, 2011, Zagreb. In this study, some key aspects of the breeding performance of the pied wagtail are reported for the first time in northwestern Croatian. Only first clutches are included. The average egg length was 20.04 mm, breadth = 14.96 mm, volume = 2276.41 mm3 and egg ...

Theories of clutch size determination have focused on first broods or on seasonal trends in clutch size. Clutch size is controlled by combination of genetic, ontological and environmental factors (KENNEDY & WHITE, 1991). In recent years, an increasing number of studies have demonstrated the existence of significant repeatability in ecologically important traits in natural bird populations (e.g....

Clutch size commonly decreases with increasing elevation among temperate-zone and subtropical songbird species. Tropical songbirds typically lay small clutches, thus the ability to evolve even smaller clutch sizes at higher elevations is unclear and untested. We conducted a comparative phylogenetic analysis using data gathered from the literature to test whether clutch size varied with elevatio...

random regression models (rrm) have become common for the analysis of longitudinal data or repeated records on individual over time. the goal of this paper was to explore the use of random regression models with orthogonal / legendre polynomials (rrl) to analyze new repeated measures called clutch size (cs) as a meristic trait for iranian native fowl. legendre polynomial functions of increasing...

Female insects have a limited energy budget to invest in reproduction. Clutch size and egg size are two traits typically involved in energy budget trade-offs, and an optimum clutch size is generally predicted. This trade-off, however, is influenced by many factors including the probability of egg parasitism. We studied this possibility in the pine processionary moth (Thaumetopoea pityocampa), w...