Skua monitoring at Rothera

What skua monitoring at Rothera does

The small population of south polar skuas at Rothera Point (up to 25 pairs) has been studied since the late 1990s.

The work began to check whether  activities around the research station were affecting the birds. Over time, the data has also revealed changes linked to prey availability at sea and to shifts in sea-ice cover.

Between 1999 and 2005, scientists monitored the population size and breeding success (measured as chicks fledged per pair).

From 2006 onwards, more detailed breeding data was collected. These include:

• laying dates
• clutch size
• egg size
• hatching success
• fledging success
• chick condition
• adult attendance (used to measure foraging effort)

Ringed south polar skua (Credit: Richard Phillips)

Since the 2007 to 2008 season, colour-ringed adults have also been tracked. These resightings provide estimates of adult survival, breeding frequency, and divorce rates. They also help build breeding histories for individual birds and show the effects of changing mates.

Monitoring chick growth rates also occurs on nearby Anchorage Island, which is used as a control site. 

Why this matters

Long-term monitoring of skuas helps scientists understand how local wildlife responds to environmental changes. Skuas are top predators, so their breeding success and survival reflect wider ecosystem conditions.

By collecting detailed breeding data, scientists can track the health of the population over time. These records also show how sea-ice changes and food availability affect the birds.

Measuring skua eggs at Rothera

How the project works

• Population counts: numbers of breeding pairs and fledged chicks are recorded each season.
• Breeding monitoring: data on eggs, chicks, and adult attendance are collected for each pair.
• Colour-ringing: adults are ringed and re-sighted to monitor survival, breeding success and pair bonds changes.
• Control colonies: chicks on Anchorage Island are also monitored to compare with Rothera.

Science objectives

The project aims to:

• measure long-term changes in skua population size and breeding success
• track adult survival and breeding behaviour using colour rings
• study the effects of prey availability and sea-ice changes on breeding outcomes
• compare skua populations at Rothera Point with nearby control colonies

Who is involved

BAS scientists monitor the skuas each year at Rothera Point. Field teams collect breeding data, monitor ringed adults, and survey the Anchorage Island population.

Science objectives

The project aims to:

• measure long-term changes in skua population size and breeding success
• track adult survival and breeding behaviour using colour rings
• study the effects of prey availability and sea-ice changes on breeding outcomes
• compare skua populations at Rothera Point with nearby control colonies

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