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E-mail address: carlosb usb. Use the link below to share a full-text version of this article with your friends and colleagues. Learn more. Although sex ratios at conception are close to in most species of birds, skewed adult sex ratios ASRs are not uncommon in populations of birds, and occur frequently at local and temporal scales. ASRs are a key variable influencing population demography, breeding systems, and many aspects of the behavior of birds.
However, factors contributing to variation in ASRs, particularly for tropical species of birds, remain poorly understood. By compiling information from field sites and records from bird collections, we found that the ASRs of four species of Columbina ground doves from Venezuela deviated significantly from parity.
Males of all species outnumbered females at all field sites and in all museum samples. ASR, expressed as the proportion of males, ranged from 0. Our samples included birds collected as specimens over many decades and across broad geographic areas, suggesting that skewed ASRs are characteristic of Venezuelan ground doves.
Because these ground doves do not exhibit pronounced sexual size dimorphism and have socially monogamous breeding systems, selection would be expected to favor equal investment in males and females at hatching. Nonetheless, skewed adult sex ratios hereafter, ASRs are not uncommon in populations of birds Donald Most studies, however, have focused on species of birds at temperate latitudes so much less is known about ASRs in populations of birds at tropical latitudes e.
To further examine the generality of this finding, we inspected Venezuelan specimens in several bird collections and confirmed a consistent bias in the ASR of all four species. Male Ruddy Ground Doves were on average 7. The museum samples covered extensive periods and broad geographical areas. We expressed sex ratios as the proportion of males in the population Wilson and Hardy , and tested statistical significance of possible deviations from parity 0.