Global warming and body mass decline in Israeli passerine birds

Abstract

Global warming may a¡ect the physiology, distributions, phenology and adaptations of plants and animals. In Israel, minimum summer temperatures increased by an average of 0.26 8C per decade during the second half of the 20th century. Bergmann's rule predicts that, in warm-blooded animals, races from warm regions are smaller than races from cold regions. Numerous studies have reported general correlations between body mass in fossil animals and independently established palaeoclimatic changes from various parts of the world in accordance with this rule. Using museum specimens, I tested the prediction that the body mass and tarsus length of ¢ve resident passerine species in Israel declined between 1950 and 1999. The body mass of four species (the graceful warbler Prinia gracilis, the house sparrow Passer domesticus, the yellow-vented bulbul Pycnonotus xanthopygos and the Sardinian warbler Sylvia melanocephala, but not of the crested lark Galerida cristata) declined signi¢cantly during this period. Tarsus length also declined signi¢cantly during this period for two species (the graceful warbler and the house sparrow). Body condition (body mass-to-tarsus length ratio) decreased in the Sardinian warbler, the yellow-vented bulbul and the crested lark. It is suggested that the above declines in body mass and tarsus length are due to global warming and also in accordance with Bergmann's rule. The above explanation does not exclude the possibility that other factors, such as a decrease in food availability, contributed to the decline in body mass. These declines may have serious implications for community structure and competition among bird species and may a¡ect the survival of small passerines.

Testing Mechanisms of Bergmann’s Rule: Phenotypic Decline but No Genetic Change in Body Size in Three Passerine Bird Populations

“…In contrast to Allen's rule, however, other studies have noted a decline in tarsus length with increasing temperatures (Yom-Tov 2001;Teplitsky et al 2008).…”

Wintering French Mallard and Teal Are Heavier and in Better Body Condition than 30 Years Ago: Effects of a Changing Environment?

“…Increase in mean body size at the population level has been demonstrated in some species Yom-Tov 2004, 2005;Yom-Tov et al 2008; review in Millien et al 2006), though the opposite has also been reported (e.g. Smith et al 1998;Yom-Tov 2001;Yom-Tov et al 2006a). Increased body mass has been reported in wild bird populations, probably a combined effect of greater food availability and lower energy demands (e.g.…”

Temperature during egg formation and the effect of climate warming on egg size in a small songbird

“…This is because egg size is only one of the traits that may be affected by climate warming (Both and Visser, 2005), among many others that may be phenotypically and genetically correlated with it (e.g. individual size or condition; see Potti, 1993;Smith et al, 1993;Williams, 1994;Christians, 2002;Yom-Tov, 2001;Lifjeld et al, 2005). Furthermore, adjustment of egg size to changes in environmental phenology, if any, will depend to a certain degree on a previous adjustment of bird phenology to the phenology of the changing environment.…”