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?
Though the solstice was more than three weeks ago the sun still hasn’t set in the Arctic. Some arctic animals have no circadian rhythm because there’s no light/dark cycle. What do the birds do?
The Max Planck Institute of Ornithology studied four species that nest near Barrow, Alaska. What they found is that some stayed on a 24-hour clock while others had no daily pattern. Their circadian rhythms varied based on lifestyle, sex and breeding stage. Here are the four they studied:
Semi-palmated sandpipers are totally monogamous and share incubation and child rearing.
Pectoral sandpiper males have multiple wives. Only the females incubate and take care of the kids.
Red phalaropes reverse these roles. The females have multiple husbands. Only males incubate and raise the kids.
Lapland longspurs are monogamous with the occasional male having multiple mates. Both parents take care of the kids but only the female incubates.
During the courtship period the shorebirds showed no daily pattern while the lapland longspurs simplified their lives by never giving up their 24-hour clock.
Incubation changed the shorebirds’ clocks. In summertime the ground temperature in Barrow varies daily from near freezing (11:00pm to 7:00am) to 60 degrees F (noon to 6:00pm). As soon as incubation began the incubating parents — pectoral sandpiper females and red phalarope males — began to follow a daily clock so they’d be on the nest when it’s cold.
The exception were the semi-palmated sandpipers. Because they completely share parental duties they threw out the clock when incubation began and synched as couples. “Who cares what time it is. We have each other.”
Meanwhile the pectoral sandpiper males and red phalarope females never stopped courting so they never developed a daily rhythm.
In the end the study shows that arctic-nesting birds are very flexible. They can be active regardless of time of day, then alter their circadian clocks when their needs change.
Those needs will change soon. The sun will set for the first time on August 1 and the birds will prepare to leave. For some shorebirds, migration has already begun.
Browsing through photos on Wikimedia Commons, this portrait of a falcon caught my eye. He’s one of six species of falcons found in Australia, new to me because he doesn’t occur in North America. The only falcon we all have in common is the peregrine.
The brown falcon (Falco berigora) is slightly smaller than a peregrine and has a different lifestyle. Rather than capture prey in the air he uses a perch-and-pounce method to capture small mammals, lizards and snakes, small birds, and insects. This is similar to the red-tailed hawk’s hunting technique.
Brown falcons don’t need to fly fast. Their wing beats are slow and they glide in a shallow V the way northern harriers do.
Though they share characteristics with hawks, Perth Raptor Care says they have a lot of personality. Click here for a video at Arkive.org that gives you a window on the lives of brown falcons: contending with crows, sharing with a mate, feeding the “kids.”
I love their brown pantaloons.
(photo from Wikimedia Commons. Click on the image to see the original)