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Phenology is one of the first processes affected by climate change and there is widespread evidence that laying date in birds advanced in response to warming temperatures in several areas. However, when all trophic levels do not respond at the same speed, this may lead to a trophic mismatch. In Europe, some insectivorous birds advanced their laying date but the date of peak insect abundance has advanced even more, leading to a mismatch between peak food availability and the peak in energy requirement of young at the nest. Thus, as climate has warmed, the selection for earlier breeding has increased but the inability of some populations to adjust to these changes has been linked to decline in numbers, though not in others. In snow geese, we previously showed that (1) there is a selection differential (i.e. difference between laying date yielding the highest reproductive success [RS] and the population mean laying date) favoring an earlier laying date; (2) RS is reduced in years of early, warm spring because plants grow more quickly, leading to a trophic mismatch between goslings hatch and peak in plant nutritive quality; but (3) despite a warming trend, laying date did not advance. I thus hypothesize that the selection differential for laying date has increased over time in snow geese (Chen caerulescens atlantica). Support for this hypothesis would indicate that some arctic birds are failing to adapt to warming temperature and are thus threatened by global change. We will calculate RS (number of young surviving to first winter) for each laying date annually and the annual selection differential by the difference between the mean laying date weighted for the number of recruits (i.e. laying date yielding highest RS) and the mean population laying date. The selection differential will be regressed over time for a 25-yr period (1991-2014). We will also examine if conditions encountered during spring migration could prevent geese from adjusting their laying date to environmental conditions prevailing at the breeding site. NDVI, a remote sensing index of plant green-up that we validated will be used to assess annual mismatch between timing of goose reproduction and plants.