Sometimes organisms are slow to adapt. In Holland’s Hoge Veluwe Park, caterpillars are maturing earlier each year as spring comes earlier. But their predators, great tits (Parus major), aren’t always changing their schedule to hatch when the caterpillars are at their peak, and bird numbers are dropping. As with the hibernating mosquitoes, great tits have a genetic trigger that spurs them to lay eggs when spring arrives. But there’s some variation in how much an individual bird can tweak its egg-laying date in response to an earlier spring. A study of 833 great tits in Hoge Veluwe over 32 years did find greater genetic selection for birds that could vary their egg-laying time to match the caterpillars' arrival. If this trend continues, it could save them from decline, but it remains unclear whether they can change fast enough to beat rising temperatures.