Variation in reproductive life-history traits of birds in fragmented habitats: A review and meta-analysis

The effects of habitat fragmentation on the distribution and abundance of birds is a well-researched topic but there is little information published in terms of how habitat fragmentation affects reproductive life history traits. We reviewed the available literature on this subject and found that only 8% of the 1,433 studies dealing with birds in fragmented habitat studied life history traits and only 1.3% provided appropriate data to perform statistics. We found no effect of fragmentation on clutch and brood size patterns. Those patterns did not change when corrected by phylogeny. However, there is a significant heterogeneity among species responses, thus data on large-bodied, ground-nesting, and precocial birds suggest an increasing response in brood size in fragmented habitats. Finally, our review shows that despite birds being the most studied vertebrate group, crucial information such as the effects of habitat fragmentation on life history traits is still scarce and insufficient, especially on species of conservation concern. Indeed, only one out of 15 species reviewed here was threatened. Studies on reproductive, behavioural and life history trait variation are urgently needed in order to advance conservation actions.