Background
Many people are worried that, as the world warms, mismatches may occur among various life cycle stages of earth's plants, the insects that feed upon them, and numerous species of animals, such as birds, that feed upon insects and provide them as food for their young; and the authors note, in this regard, that "the increasing mismatch between great tit Parus major laying dates and their caterpillar food supply in the Netherlands has rapidly become a classic example of a lack of adaptation to climate change," citing the work of Visser et al. (1998, 2006) and Visser (2008). However, they report that "other populations of the same bird species have subsequently been shown to advance their laying dates much more strongly," in order to match the earlier spring growth of vegetation that typically occurs during periods of extended warming, citing Cresswell and McCleery (2003) and Charmantier et al. (2008); and they go on to describe their own study that brings a further degree of clarity to the subject.

What was done
Matthysen et al., as they describe it, "studied the breeding cycle of two sympatric and closely related species, the blue tit Cyanistes caeruleus and the great tit Parus major in a rich oak-beech forest," where they had collected data on the breeding biology of blue and great tits from 1979 to 2007 in a 12-hectare plot provided with nest boxes inside the Peerdsbos forest near Antwerp, Belgium.

What was learned
The three researchers report that both bird species "advanced their mean first-egg dates by 11-12 days over the last three decades," and that "the time from first egg to fledging has shortened by 2-3 days, through a decrease in laying interruptions, incubation time and nestling development time." As a consequence, they say "the average time of fledging has advanced by 15.4 and 18.6 days for blue and great tits, respectively, and variance in fledging dates has decreased by 70-75%." Most important of all, they note that "indirect estimates of the food peak suggest that both species have maintained synchronization with the food supply," and they state that "analyses of within-individual variation show that most of the change can be explained by individual plasticity in laying date, fledging date and nest time."

What it means
Matthysen et al. emphasize that "synchronization of the nestling period with the food supply not only depends on first-egg dates but also on additional reproductive parameters including laying interruptions, incubation time and nestling growth rate." And as a result of adjustments in these several related phenomena, they report that "both of our study species have been able to maintain synchrony with their food supply in the face of global warming."

References
Charmantier, A., McCleery, R.H., Cole, L.R., Perrins, C., Kruuk, L.E.B. and Sheldon, B.C. 2008. Adaptive phenotypic plasticity in response to climate change in a wild bird population. Science 320: 800-803.

Cresswell, W. and McCleery, R. 2003. How great tits maintain synchronization of their hatch date with food supply in response to long-term variability in temperature. Journal of Animal Ecology 72: 356-366.

Visser, M.E. 2008. Keeping up with a warming world; assessing the rate of adaptation to climate change. Proceedings of the Royal Society B-Biological Sciences 275: 649-659.

Visser, M.E., Holleman, L.J.M. and Gienapp, P. 2006. Shifts in caterpillar biomass phenology due to climate change and its impact on the breeding biology of an insectivorous bird. Oecologia 147: 164-172.

Visser, M.E., van Noordwijk, A.J., Tinbergen, J.M. and Lessells, C.M. 1998. Warmer springs lead to mistimed reproduction in great tits (Parus major). Proceedings of the Royal Society B-Biological Sciences 265: 1867-1870.