Phenological Mismatch: Migration Timing vs. Food Peak

Climate Warming

Warming above baseline 0.0 °C

≈ baseline period (1980s)

Timing cues

Food peak day (temp-triggered)

–

Hatching day (day-length cue)

–

Mismatch: hatching − food peak

–

Consequence for the brood

Food availability at hatching

–

Offspring survival rate

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How it works

Two independent clocks drive this system. The insect food burst tracks spring temperature — as the climate warms, the whole curve slides earlier on the calendar. The migratory bird's arrival and brood-hatching date tracks day length, a cue that a warming atmosphere does not change, so it stays essentially fixed year after year.

Historically the two lined up: hatching fell right on the shoulder of the food peak. As warming grows, the temperature-driven peak keeps sliding earlier while hatching stays put, so by hatching day the burst has already crested and is fading — less food exactly when chicks need the most.

Food curve ≈ Gaussian burst; peak shifts ~6 days earlier per °C of warming.
Hatching date is fixed by photoperiod, independent of temperature.
Food availability at hatching = the burst's height on hatching day.
Survival rate scales with that food availability, with a low floor for near-total mismatch and a high ceiling when timing is aligned.

Food-source abundance Hatching date (fixed) Food peak (shifting)