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Author: Reuven Yosef

Use of flock members to reduce individual levels of vigilance has been the focus of many studies that have attempted to explain the relationship among vigilance, group size, and distance covered by using foraging or preening as indicators. To avoid the confounding variables associated with foraging and preening, the effects of increasing levels of disturbance on vigilance by measuring distances among individuals (D) in flocks of greater flamingoes was studied. During 61 h, reactions to 112 disturbances were recorded. Undisturbed flamingoes exhibited no relationship between D and flock size. When joggers appeared, birds became alert but continued to feed. D was uninfluenced by flock size when jeeps drove past, but was different in value from that in undisturbed flocks. However, when tours stopped and occupants got out of their vehicles, D was significantly reduced and flock size was positively correlated with flock cohesiveness, i.e., smaller flocks had smaller D values than larger flocks. Flamingoes were terrified of all-terrain vehicles, and in 82% of these encounters, they flew away. In these cases, flock cohesiveness was extremely dense, but flock size did not influence flock reaction. This study shows that flocking species seek protection in numbers, and they leave the area when insufficient conspecifics are present when serious disturbance occurs.

In: Israel Journal of Ecology and Evolution
In: Israel Journal of Ecology and Evolution
Authors: Amnonn Hahn and Reuven Yosef

Abstract

Following extensive renovation of urban areas of central Israel, and in the framework of a research project of supplying nest-boxes for urban breeding birds, especially Common Swifts Apus apus, we documented interspecific nest destruction by House Sparrows Passer domesticus. In two separate incidents the House Sparrows entered the nest chamber of the swifts and removed the eggs by puncturing them. In one, the incident occurred early enough in the breeding season and allowed the Common Swift pair to renest and successfully fledge two young.

In: Israel Journal of Ecology and Evolution

The Levant sparrow hawk (Accipiter brevipes) is a typical raptor with reversed sexual size dimorphism wherein the female is larger than the male. Here, we present the factors contributing to biometric differences between the age and sex classes. Starting from 1984, 1164 Levant sparrow hawks were captured and banded in the area immediately to the north of Elat, Israel. Comparing mean values, feather-dependent characters were 6.6–7.3% larger in adult females than in adult males, and 6.2–6.8% larger in second year females than in second year males. Differences were greater for culmen and hallux length and for body mass. We found wing cord and body mass to be the parameters most efficient in separating sex or age classes. Upon performing discriminant analyses on our data set, we found that hallux length varied independently between males and females, irrespective of the age of the bird. Our data establish that the Levant sparrow hawk is the least dimorphic of the European Accipiter species but has a sex-specific hallux size.

In: Israel Journal of Ecology and Evolution

The wryneck is an unusual representative of Palearctic Picidae in that it is a long-distance migrant, whose populations have declined across Europe in the last century. Israel is at the eastern extremes of the known wryneck migration routes in the spring, which are little studied. Hence, we studied the species migration patterns and staging at Eilat, the southern tip of Israel being a very important stopover site for many migratory bird species. During 28 springs and 25 autumn migration seasons in the years 1983-2010, a total of 588 wrynecks were trapped.

The mean number of birds recorded per spring season was 18.32 (SE = 2.12) and only 3.00 ± 0.71 per autumn season. The analysis performed for spring passage showed that the mean proportion of juveniles to all birds to which ages were assigned was 48.9 ± 5.2%. Furthermore, we did not find any differences in the dates of ringing, wing length, body mass or body condition index of juvenile and adults. We retrapped 97 (18.9%) wrynecks during the spring. The average proportion retrapped per season was 18.3 ± 2.9% and the average stopover was 4.8 ± 0.4 days. Recaptured birds were in better body condition than at first capture, and the body condition index gained significantly during their stay at the stopover site. The low conservation priority accorded to these habitats — and ignored in spite of many studies from the reagion — highlights the importance of the preservation of priority areas such that avian and other migrations can continue with minimal human impact.

In: Israel Journal of Ecology and Evolution