Two breeding colonies located in the most north-eastern corner of Greenland—at Amdrup Land (80°50′N/14°37′W) and Station Nord (81°35′N/16°39′W)—were monitored (see Gilg et al. 2009 for details on ivory gull breeding sites and numbers in Greenland). The Amdrup Land colony is located on a flat rocky plateau surrounded by glaciers, about 5 km inland. The Station Nord colony is located on a coastal terrace, at about 3 km from a military station, where birds are nesting about 1 km from the year-round ice-covered Arctic Ocean. The sea of this part of Greenland is covered by multiannual drift ice throughout the year, yet localized and predictable bodies of open water, like the North-East Water Polynya, make the region attractive to breeding ivory gulls. The ivory gull usually lays one to two eggs, more rarely three eggs (Mallory et al. 2008). Both parents incubate nests for 24–26 days, eggs typically hatch in mid-July in North Greenland and chicks fledge 30–35 days after hatching.

The two colonies were visited during the hatching period. The Amdrup Land colony was visited on four occasions between 25 July and 1 August 2009. The Station Nord colony was visited on two occasions on 4 July and 9 July 2011. For each colony, we monitored the number of occupied nests, laid eggs and hatched chicks. The colonies were not monitored during the storm peak; the breeding failure was assessed by an active survey of the colony the day following the storm. Weather data (temperature and precipitation) were automatically collected by the Danish Meteorological Institute at Station Nord for the period 1961–2011 (Capellen 2012). We used linear regression (for temperature) and general linear model (for precipitation, with a quasi-poisson family model) to examine temporal trends in the data over the past 50 years.

A total number of 96 nests were occupied at Amdrup Land during our first visit (25 July 2009; Table 1). The brood size was one (n=49 nests) or two (n=41 nests). For six nests, we were unable to assign already highly mobile chicks to a nest. An average of 1.46±0.50 offspring were produced per nest. On 28 July 2009, around 21:00 local time, a rainy storm started and lasted for 18 hours. Twelve hours after the start of the heavy rain at 09:00 on 29 July, a windstorm rose up that lasted for 36 hours. On 31 July 2009, an active survey of the colony found only two live chicks; these were abandoned chicks hidden in stony crevices. Many chick carcasses (n=36) were found in and around nest cups, with for some, apparent signs of pecking from adults on the body. All eggs that could still be found were crushed in or near the nests. While most adults were still present in a large flock near the colony, all 96 nests were unattended. Given the null chances for these two last downy chicks to survive without parental care, breeding failure can confidently be estimated as being 100%.

A total of 50 nests were occupied in the breeding colony on 4 July 2011 (Table 1). The mean clutch size was then 1.64±0.52 offspring (Table 1). From 5 to 8 July 2011, heavy snow and rains hit the region. On 9 July 2011, when visiting the colony for the second time, none of the previously occupied nests were still active. Neither eggs nor chicks were found in the nests and only a few adults were present in the colony. A second group of birds was breeding a little further from the main colony (nest occupancy checked by scope sighting) but nest content was only monitored after the storm. Here again, none of the 26 occupied nests were active.

For the period 1961–2011, the air over land warmed by 2.75°C for the month of July at Station Nord (coefficient β=0.066, standard error [SE]=0.003; F _1,40=68.17, P<0.001; Fig. 1a). For the same period, the five-year moving average annual rainfall recorded indicates a significant increase in the precipitation regime (β=0.007, SE=0.002, F _1,40=6.79, P<0.013; Fig. 1b).