As things stand now this intelligent, resourceful, omnivorous bird may go extinct in the 21st century. Why? Because he lives in a shrinking bubble.
For a long time scientists could not figure out why the Ethiopian bush-crow (Zavattariornis stresemanni) lived in only one 6,000 square mile area of southern Ethiopia. He’s really smart, eats anything, and nests cooperatively but the bush-crow does not expand his range even though the habitat bordering his domain appears to be exactly the same.
His size and threatened lifestyle resemble that of the Florida scrub-jay whose range was 7,000 square miles but an area of suitable habitat much smaller. Scientists approached the bush-crow with the same tools they used on the scrub-jay and came up empty. The bush-crow’s bordering habitat was the same. Why didn’t the bush-crow use it?
Then in 2012 a team headed by Dr Paul Donald of the RSPB figured out that the Ethiopian bush-crow lives in a cool, dry climate bubble where the average temperature is less than 20oC (68oF). Outside his range it’s hotter and he won’t go there. Terrain and elevation created his zone but climate change is raising the temperature and the bush-crow’s bubble is shrinking.
If his problem was caused by loss of habitat, as it is for the Florida scrub-jay, laws and habitat restoration could increase the bush-crow’s available land but climate change is a much thornier problem requiring international political will. This bird is endangered.
Right now there are about 9,000 breeding pairs of Ethiopian bush-crows on earth. But for how long?
Click here to read about the Ethiopian bush-crow’s climate preference. Click here for his range map.
(photo from Wikimedia Commons. Click on the image to see the original)
Snakes seem to be a subtext on my blog lately. Snakes caused the extirpation of the Guam rail, they’re one of many foods eaten by secretary birds, and now I’ve learned there’s a falcon in Central and South America that eats poisonous snakes and laughs.
The laughing falcon (Herpetotheres cachinnans) is named for his two most obvious traits. Herpetotheres roughly means to “mow down snakes,” cachinnans means to “laugh immoderately.”
He captures snakes by watching from a perch, then pouncing to break their necks or behead them. And he really does laugh. Listen to this recording of a pair “singing” a duet.
Laughing falcons are about the size of peregrines and are often pictured with their head feathers raised, a pose that makes them resemble ospreys not falcons. When they lower their head feathers, as in this photo on Wikimedia Commons, you can see their falcon family resemblance.
I first heard of this species when Charlie Hickey posted photos from his trip this month to Puntarenas, Costa Rica. (Click here for Charlie’s photos.) I wonder if it was hard to find this bird in Costa Rica. According to BirdLife International the laughing falcon has declined drastically in some locations but has such a wide range that it has not yet been listed as “vulnerable.”
Birds love to perch on wires and power poles, the bigger the bird the bigger the wire. Unfortunately this affinity poses a threat to very large birds because their long wings can touch two wires at the same time and electrocute them. Vultures are especially vulnerable because they roost in large gregarious groups. If they jostle their buddies too much … ooops!
Cape vultures (Gyps coprotheres) of southern Africa, like most Gyps species, are declining. They are listed as threatened because of decreased carrion for their chicks, poisoning from medication in livestock carcasses, electrocution and collision with wires, and exploitation for traditional medicine/religion.
Cape vultures live a long time and reproduce slowly so significant losses of any kind pose a problem. There are protected areas in southern Africa where the vultures aren’t exposed to so many threats but there is also a growing power grid.
W. Louis Phipps and his team decided to find out how cape vultures used the power grid so they affixed GPS trackers on nine cape vultures — five adults and four immatures — to see where they would go. The results were somewhat surprising.
The cape vultures’ home range is larger than expected; some traveled more than 600 miles one way. Given the opportunity to travel the power corridors, that’s what they did. Cape vultures are cliff birds so the power towers gave them high perches and clear sight lines in formerly useless habitat. The study also found that the vultures fed more often on private farmland than in protected areas. (The vultures would say, “Well, that’s where the food was.”)
It’s the classic Catch-22. The power corridors have expanded the cape vultures’ range but the wires sometimes kill them. In a declining population it makes a difference.
Some raptors have special techniques for finding food. This one has used trains and motorcycles.
Aplomado falcons (Falco femoralis) are native to grassland and marshland from Mexico to South America where they eat birds, insects and small vertebrates. Sometimes they hunt while soaring or from a perch but when hunting birds they prefer to fly fast through thickets to flush them from cover. This technique is similar to a Coopers hawk.
Mated pairs like to hunt cooperatively. The male makes a distinctive “chip” sound to call his mate to a hunt. Sometimes the female will even come off the nest to participate. The male corners the prey by hovering above the thicket. The female flies through and flushes it.
When his mate can’t come out to hunt, what’s a guy to do? Borrow a motorcycle.
Aplomados have figured out that our large, loud vehicles scare small birds into flight. According to Birds of North America online, one researcher reported an aplomado following a motorcycle to pick off small birds flushed from the side of the road. Another reported a falcon flying with a train and switching sides to check out the ditches.
These falcons were extirpated from the U.S. in the 1950′s and only recently made a comeback in New Mexico and south Texas, partly on their own and partly thanks to reintroduction programs.
When I travel southwest to find an aplomado I wonder … will it help to watch for motorcycles?