Concomitant Patterns in Avian and Mammalian Body Length Changes in Denmark

Niels Martin Schmidt, Royal Veterinary and Agricultural University
Per Moestrup Jensen, Royal Veterinary and Agricultural University

DOI: http://dx.doi.org/10.5751/ES-01372-100205

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Abstract

We gathered length data on 61 Danish breeding birds from the past 200 years, and related the pattern of change to present body mass and other ecological parameters. Body mass was the only parameter significantly correlated with the rate of change, and the emerging pattern in the rate of change followed the island rule. That is, smaller species have become larger and vice versa, while the medium-sized species remain essentially unchanged. The suggested optimal body mass was around 85 g. Though orders of magnitude lower, the pattern in avian body size change was similar to that of Danish mammals. Our analyses suggest that increasing habitat fragmentation leads to altered body size towards being medium-sized in Danish vertebrates. The changing landscape, thus, appears to be an important driver of body size changes in vertebrates.

Key words

Body length; habitat fragmentation; island biogeography; island rule; Aves; reproductive output; migration; feeding category; competition; avoidance; tolerance.

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