Alaska's birds could see danger from the parasitic Russian cuckoo invasion

A common cuckoo chick. Photo by Tomas Grim.
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ANCHORAGE (KTUU) - A particularly dangerous species of bird has been spotted living and mating in Alaska recently, and experts say that could spell disaster for the local bird ecosystem.

The birds in question are the common cuckoo and the oriental cuckoo – inhabitants of Siberia and other parts of eastern Russia.

The cuckoos are known as "brood parasites," which means that they rely on others to raise their young. However, the way they do it is "vicious."

"They are quite vicious – we call them virulent," said Mark Hauber, ornithologist at the University of Illinois, and leader of research developing on the cuckoo's presence in Alaska. "They are just like diseases or bacteria or viruses, in that the impact is to reduce the breeding success of their host."

Basically, the cuckoo will lay its eggs in the nests of other bird species, and then leave. It will never hatch or raise its own offspring. Instead, their eggs will be incubated by the bird at the host nest.

The reason cuckoo eggs sometimes succeed, even by birds aware of the strategy, is that cuckoo eggs are typically camouflaged to blend in among the host's own eggs; consequently, they are often very hard to tell apart from other eggs.

After the cuckoo chicks hatch – an incubation usually timed out by the cuckoo so that the cuckoo chicks hatch earlier than the other eggs in the nest – the young cuckoo chick will kill the other eggs, leaving it alone in the nest.

This strategy of population is rare, Hauber says, with less than 1 percent of all birds exhibiting this form of reproductive habit. Though rare, it can be devastating to an unsuspecting bird population, as it completely disrupts the breeding cycle as entire generations of birds are eliminated in this way.

While much of the activity of the cuckoo is well researched, a problem has been recently identified by Hauber and his team.

The cuckoo is expanding its breeding range into western Alaska. While birds in Siberia and Asia are aware of the cuckoo and its habits, and have developed defenses against it, birds in Alaska are unaware and very vulnerable to the pattern.

Hauber and his team devised a way to determine whether Alaska birds would be prepared for the cuckoo threat, and according to the data, Alaska's birds failed miserably.

The researchers 3-D printed replica eggs of the cuckoo, and placed them in nests both in native eastern Russia and Alaska – indicated in this video.

A majority of the host birds in Europe either destroyed the 3-D printed eggs, or pushed them from the nest, realizing they were the parasitic cuckoo or otherwise did not belong. In Alaska, however, out of the 96 eggs placed into host nests, just one bird kicked out the test egg.

"Birds in the Lower 48 or Siberia have evolved responses to this threat," Hauber said. "The Alaska birds have no behavioral response to the presence of strange or foreign eggs in their nest. We didn't even need to run statistics. The numbers speak for themselves in this case."

While the threat to Alaska birds could be devastating to population sizes, so far no eggs have been found in Alaska nests. But that doesn't mean these parasite eggs aren't in Alaska nests. Hauber said that fact is more than likely.

Cuckoos have been recently spotted in Alaska both living and mating. Hauber said this suggests there are eggs in Alaska, but they may just be hard to find.

When a cuckoo egg is found in the wild, Hauber said the researcher that finds it will likely get some fame.

"Whoever finds the first cuckoo egg in a host nest in Alaska is going to get another paper published," Hauber said.

After that, it will be up to Alaska's bird population to – like Russian songbirds – develop their own strategies for avoiding the trap. In fact, Alaska's birds might already be fighting back unwittingly.

"Birds are quite adaptable," Hauber said. "The cuckoo looks like a sparrowhawk, so people have already seen native birds in Alaska attack adult cuckoos. It's possible that they will quickly pick up on the fact that the nest is in danger, and they should defend their nests against this new threat."


A cuckoo egg hides among bluethroats eggs. Photo by Kristaps Sokolovskis.
An artificial cuckoo egg planted in a pipit nest. Photo by Harald Ris.
A cuckoo egg blending in to a redstart nest. Though the egg matches the color palette, it is noticeably larger. Photo by Tomas Grim


 
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