Methods Details:

Monthly sea surface temperature (SST) time series were derived from three Level-4, gap-filled global SST products: the Multi-scale Ultra-high Resolution SST (MUR SST; Chin et al., 2017), the Operational SST and Sea Ice Analysis (OSTIA; Donlon et al., 2012), and the Optimum Interpolation SST (OISST; Huang et al., 2021).

For each seabird colony, a 200-km circular buffer was generated around the nesting site coordinates. SST data within this area were extracted at each monthly time step. To exclude land, a land mask derived from the MUR SST mask variable was applied at the appropriate spatial resolution for each dataset. For colonies located in regions with seasonal sea ice, an additional ice mask was calculated for each time step by assuming that missing ocean data (not flagged as land) represented ice-covered areas. These ice masks were computed separately for each dataset and combined with the circular and land masks.

SST data from ice-free ocean pixels within the masked region were averaged spatially and aggregated to monthly means, producing a continuous SST time series for each colony. For each site and dataset, both mean and standard deviation were calculated. All data acquisition and processing were performed in Python using the xarray library.

Sampling Site Details:

Sea surface temperature data were extracted for 22 premier seabird colony sites worldwide (listed below), each defined as a location with a high density of seabird nests and at least two species with reproductive success time series spanning more than 25 years. For each site, a 200-km circular sampling area was centered on the colony coordinates.

Admiralty; Latitude: -62.1778°; Longitude: -58.4447°
Aiktak; Latitude: 54.1886°; Longitude: -164.8400°
Bird; Latitude: -54.0056°; Longitude: -38.0500°
Buldir; Latitude: 52.3581°; Longitude: 175.9247°
Cape Peirce; Latitude: 58.5528°; Longitude: -161.7690°
Chowiet; Latitude: 56.0342°; Longitude: -156.7012°
Crozet; Latitude: -46.4167°; Longitude: 51.8333°
Foula; Latitude: 60.1385°; Longitude: -2.0793°
Hornøya; Latitude: 70.3877°; Longitude: 31.1553°
Isle of May; Latitude: 56.1858°; Longitude: -2.5575°
Kerguelen; Latitude: -48.4000°; Longitude: 68.3667°
Middleton; Latitude: 59.4382°; Longitude: -146.3266°
Pointe Géologie; Latitude: -66.6667°; Longitude: 140.0167°
Røst; Latitude: 67.5200°; Longitude: 12.0989°
Southeast Farallon; Latitude: 37.7249°; Longitude: -123.0303°
Seal Island NWR; Latitude: 43.8876°; Longitude: -68.7408°
Shetland; Latitude: 60.4100°; Longitude: -1.2600°
Signy; Latitude: -60.7170°; Longitude: -45.6000°
St. George; Latitude: 56.5743°; Longitude: -169.6130°
St. Lazaria; Latitude: 56.9872°; Longitude: -135.7047°
St. Paul; Latitude: 57.2044°; Longitude: -170.2830°
Talan; Latitude: 59.3107°; Longitude: 149.0829°
Teuri; Latitude: 44.4167°; Longitude: 141.3000°