ost seabirds breed on islands where they are safe from terrestrial predators - or at least they were until people started moving rats and cats and other commensal species around the planet. By breeding on islands, seabirds can occur at high densities, gaining social benefits from foraging together and sharing colony defence against avian predators such as skuas or gulls.
However, one drawback to having large numbers of birds breeding together in the same place year after year is that seabird colonies often accumulate high densities of parasites. Mostly this ancient conflict between host and parasite goes on unnoticed, but in the past few decades we have come to appreciate how internal parasites and diseases have major evolutionary implications for seabirds.
Ectoparasites are more readily detected - seabird biologists have a wealth of anecdotes about the challenges posed by ticks and fleas on seabird islands.
The brooding Cape Gannet (left bird) speckled with feather lice prepares to greet its mate, which lacks any visible lice. Seconds later, the partner also has lice on its feathers (right).
This story is from the January/February 2023 edition of African Birdlife.
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This story is from the January/February 2023 edition of African Birdlife.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 9,000+ magazines and newspapers.
Already a subscriber? Sign In
EXPLORING NEW HORIZONS
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winter wanderer
as summer becomes a memory in the south, the skies are a little quieter as the migrants have returned to the warming north. But one bird endemic to the southern African region takes its own little winter journey.
when perfect isn't enough
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The late summer period naturally started quietening down after the midsummer excitement, but there were still some classy rarities on offer for birders all over the subregion. As always, none of the records included here have been adjudicated by any of the subregion's Rarities Committees.
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One of the features of a warming planet is increasingly erratic rainfall; years of drought followed by devastating floods. Fortunately, many waterbirds are pre-adapted to cope with such extremes, especially in southern Africa where they have evolved to exploit episodic rainfall events in semi-arid and arid regions. But how do waterbirds respond to floods in areas where rainfall - and access to water - is more predictable? Peter Ryan explores the consequences of recent floods on the birds of the Western Cape's Olifants River valley.
a star is born
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