Influence of climate on reproductive success in Mexican Jays

Sh. Li et Jl. Brown, Influence of climate on reproductive success in Mexican Jays, AUK, 116(4), 1999, pp. 924-936
Citations number
Categorie Soggetti
Animal Sciences
Journal title
ISSN journal
0004-8038 → ACNP
Year of publication
924 - 936
SICI code
In the arid southwestern United States, many birds initiate breeding in the driest months of the year, March to May, long before the monsoon rains arr ive in Fly and August. Although breeding success in these species is though t to be sensitive to precipitation, the relationships have not been rigorou sly described based on long-term study of a single species. We studied the relationships among reproductive success, precipitation, and temperature in Mexican lays (Aphelocoma ultramarina) in the Chiricahua Mountains, Arizona . We identified three orthogonal factors that accounted for 85.8% of the va riance in the II reproductive-success variables, Factor 1, the most importa nt, was associated with production of young and with the fraction of female s that were breeding. Because the Mexican lay is a plural breeder (more tha n one breeding female per group), reproduction in the population can be inf luenced not only by the success of individual females, but also by the prop ortion of females in each nock that breed in a given year. This factor was positively related to the amount of precipitation both at the onset of bree ding in March and April and during the previous eight months. Brood size at banding (14 to 15 days), which was strongly associated with Factor 2, was negatively related to the number of adult females per nock and relatively i nsensitive to yearly variation in climate. Success of the youngest females was associated with Factor 3 and depended on a different set of variables t han that of older females. Although production of young was predictably dep ressed in drought years, the significant relationships between reproductive success and climate did not otherwise enable precise predictions based on climate alone. Because predation appears to be highly correlated with the n umber of nestlings per unit, the lack of strong predictability of reproduct ive success using climate variables alone may be caused by the independence of predation from climate variables.