Two large, graceful raptor species glide over the plains of the Extremadura region of Spain, but the population of one species, the Red Kite, is in serious decline, while the other, the Black Kite, is expanding its range and quickly becoming the most numerous raptor in Europe. Inquiring minds want to know why…so I consulted our fabulous bird guides (Alan Davies and Ruth Miller of birdwatchingtrips.co.uk) for an explanation.
But there is more than just morphology that differentiates these two species — behaviorally, they are quite different as well, and this is part of the reason for the difference in their abundance in the Extremadura region.
Both Kite species depend heavily on scavenging on carrion of sheep or cattle carcasses and roadkill, but also hunt live prey, gliding down and snatching them off the ground and effortlessly moving back upward to soar to a perch to eat what they have grabbed. Red Kites particularly like a diet of earthworms in the spring — strange food for such a large bird. As scavengers, Red Kites seem particularly susceptible to poisoning, from illegal baits set for other predators like foxes, which somehow Black Kites either avoid or are less affected by.
Lastly, Black Kites are a highly opportunistic species, changing their foraging strategy to suit the “prey” (including carrion) availability, and they seem to be less affected by human disturbance, even nesting in close proximity to roads and houses.
A number of reasons have been suggested for the difference in the success of these two, very similar species: susceptibility of the Red Kite to poisoning, disruption of breeding habitat for the Red Kite, availability of natural prey for the Red Kite, like mice and rabbits who are also limited by conversion of habitat to agriculture, and lastly, climate change that has resulted in drought and vegetation changes that make the landscape unsuitable for Red Kite survival. Among the laws of nature, it’s “adapt or die” to change. And the Black Kite seems to be the more adaptable.