Monday, January 18, 2010

More Raptors of Kenya: Chanting-goshawks and Buzzards

This is the fifth in a series of posts summarizing my experiences on our recent trip to Kenya to study East African Raptor Ecology. The first post was on African Fish Eagles and other wildlife at Lake Naivasha, Kenya. The second covered the Big Cats of Kenya. While not raptors, they were one of the many highlights of the trip. The third post was focused on the vultures of Maasai Mara National Park. Deviating again from the Raptor theme, the fourth post covered giraffes. In this post I will cover some more of the raptors we studied.

Dark Chanting-Goshawk. Masai Mara, Kenya.

As I mentioned in a previous post, each student in East African Raptor Ecology course was assigned an individual species to study and prepare a 30 minute presentation on. My species was the Dark Chanting-goshawk (Melierax metabates). This species, and the two others in this genus (Eastern Chanting-goshawk and Pale Chanting-goshawk) primarily occupy sub-Saharan Africa with a small population in Morocco and the Arabian Peninsula. We would see two Darks and two Easterns on our trip. The primary distinguishing factor between the two is the cere color - yellow for eastern and orange for the dark. Taxonomically this genus has been moved around quite a bit over the past 100 years. Based on the most recent published DNA analysis, it is believed that the Accipiters, the Harriers, and the Chanting-goshawks had a common ancestor. The Harriers and Accipiters being more closely related to each other than to the Chanting-goshawks. The Chanting-goshawks fulfill a similar ecological role to the Harris Hawks of the US Southwest/Mexico. They hunt both solitarily and in groups, similar to Harris Hawks. The Pale Chanting-goshawk has been documented to form Polyandrous Trios in prey rich environments. This is also a trait in common with the Harris Hawk. A Polyandrous Trio consists of an alpha male, beta male, and a single female. The alpha male usually gets 2/3 of the copulations. Apparently 1/3 is just enough to keep the beta male interested and contributing. In contrast to a monogamous pair, the trio is able to raise multiple broods per year. If the two males are related, the inclusive fitness is greatly enhanced. If they are not related, fitness matches monogamous pairs. They eat rodents, reptiles, birds, and insects. Lizards are the dominant food source.

A closely related species, in a genus of its own, is the Gabar Goshawk (Micronisus gabar). This species is sometimes considered in the Melierax genus with the Chanting-goshawks. It looks very similar, but is much smaller. It does however aggressively and successfully defend its territory against its large cousins.

Gabar Goshawk. Nairobi National Park, Kenya.

Gabar Goshawk. Nairobi National Park, Kenya.

We watched this Gabar stare down a group of Long-tailed Fiscals. Once the Gabar flew, the place erupted as many Northern Pied Babblers converged on the bush where he was perched. He must have cleared them out earlier.

At Lake Naivasha we saw many Eurasian Marsh Harriers. Maasai Mara was dominated by Pallid and Montagu's Harriers. No great photos to speak of. Most of the Falcons also eluded my camera. There were numerous Lanner Falcons and Lesser Kestrels. Some Common Kestrels and Grey Kestrels. We are pretty sure we saw a Sooty Falcon, an Ovambo Sparrowhawk, and a Great Sparrowhawk. Not a bad week. The other vehicle saw two Amur Falcons, but we missed them. There were also African Goshawks, Black-shouldered Kites, and a couple of other unidentified accipiters.

The Buzzards. I still hear many people refer to vultures as buzzards. The fact is that buzzards are buteo hawks, similar to the North American Red-tailed Hawk. In the old world, buteos are generally called buzzards, in the new world they are called hawks.

The most common buzzard in Kenya was the Augur Buzzard (Buteo Augur).

Augur Buzzard. Maasai Mara, Kenya.

The Augur Buzzard has a red tail similar to the Red-tailed Hawk of North America. It is also common enough in Kenya, that if you see a buteo, its a safe bet that its an Augur. We came upon an all black buteo at one point. We frantically flipped through multiple field guides, eventually discovering it to be a melanistic Augur buzzard. I've had a similar experience with dark morph Red-tailed Hawks in the US. Melanistic individuals have an increased amount of pigmentation in their skin/feathers. It is the opposite of leucism and albinism, which occur because of a lack of melanin or other types of pigment.

Melanistic Augur Buzard. Maasai Mara, Kenya.

Our host in Kenya performed his PhD research on Augur Buzzards. We joked that he couldn't pass an Augur Buzzard without stopping to look. This is similar to Swainson's Hawks on our ornithology class field trips last spring. Our ornithology instructor studied Swainson's hawks for his PhD. Someday I will have my students look at every bird that I studied as well! It's all in fun. They are great birds and we appreciated looking at them.

Augur Buzzard, Nairobi National Park, Kenya.

Augur Buzzard, Nairobi National Park, Kenya.

The eagles will have to wait for another day...

No comments: