Figure 11.18 The effects of habitat quality. In blue tit songbirds, deciduous downy oak forests support many more adult breeding pairs than evergreen holm oak forests. In addition, birds living in the downy oak forest produce about 60 percent more fledglings per nest.
Data from J. Blondel, Habitat heterogeneity and life-history variation of Mediterranean blue tits (Parus caeruleus), The Auk 110 (1993): 511–520.