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).
Denne historien er fra January/February 2023-utgaven av African Birdlife.
Start din 7-dagers gratis prøveperiode på Magzter GOLD for å få tilgang til tusenvis av utvalgte premiumhistorier og 9000+ magasiner og aviser.
Allerede abonnent ? Logg på
Denne historien er fra January/February 2023-utgaven av African Birdlife.
Start din 7-dagers gratis prøveperiode på Magzter GOLD for å få tilgang til tusenvis av utvalgte premiumhistorier og 9000+ magasiner og aviser.
Allerede abonnent? Logg på
EXPLORING NEW HORIZONS
Keith Barnes, co-author of the new Field Guide to Birds of Greater Southern Africa, chats about the long-neglected birding regions just north of the Kunene and Zambezi, getting back to watching birds and the vulture that changed his life.
footloose IN FYNBOS
The Walker Bay Diversity Trail is a leisurely hike with a multitude of flowers, feathers and flavours along the way.
Living forwards
How photographing birds helps me face adversity
CAPE crusade
The Cape Bird Club/City of Cape Town Birding Big Year Challenge
water & WINGS
WATER IS LIFE. As wildlife photographer Greg du Toit knows better than most.
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
Egg signatures and forgeries in the cuckoo-drongo arms race
Southern SIGHTINGS
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.
flood impact on wetland birds
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
It’s every producer’s dream to plan a wildlife television series and pick the right characters before filming.
