Abstract: Climate change is altering vegetation phenology, differentially affecting food quality and availability for the gosling development (and therefore fitness) of migratory herbivores, especially those experiencing range contraction and fragmentation. By quantifying the climate-vegetation nexus for two waterbird species of contrasting conservation status, we assessed the differential implications of climate change in semi-arid landscapes for gosling development windows in different parts of their mid-latitude breeding ranges. We defined breeding ranges using telemetry data from 663 summering tracks of tagged Swan Geese (Anser cygnoides) and Greylag Geese (A. anser) breeding across the Mongolian Plateau. Within these areas, we systematically analyzed spatiotemporal variations in vegetation phenology based on MODIS NDVI datasets from 2000 to 2024 and their response to climate factors. Combining the above data, we demonstrated synchrony between goose breeding phenology and vegetation phenological indices: gosling hatching coincided with the start of growing season (SOS), autumn migration initiation with the end of growing season (EOS). We determined temporal and geographical variation in vegetation SOS, EOS and the length of growing season (LOS = EOS − SOS) as a proxy for gosling development windows across the Mongolian Plateau. Mean LOS was 107 ± 13 days, generally sufficient for gosling development (c. 113 days), but showed spatial heterogeneity, increasing in the west but shortening in the east of Mongolian Plateau. SOS was delayed with higher land surface temperature and lower precipitation/aridity in central/eastern Mongolian Plateau, but advanced in the west. Elevation of these three climatic factors delayed EOS across Mongolian Plateau. Climate warming and hydric stress may trigger synergistic SOS-delay and EOS-advance effects in the central and eastern Mongolian Plateau, increasing differential phenological mismatch risks to offspring fitness, thereby potentially affecting population growth rates and distributions.