Nature, Science

Bird Mafia Uses Violence and Forces Other Birds to Hatch Their Eggs

Cowbirds ensure that they don't have to adapt their eggs to resemble those of other species. By threatening violence they forces the stepparents to accept their egg.
Cowbirds ensure that they don’t have to adapt their eggs to resemble those of other species. By threatening violence, they force the stepparents to accept their egg. Photo: Max Planck Institute.

Certain species of birds, like the brown-headed cowbird or the European great spotted cuckoo, lay eggs in other birds’ nest. They hope that those birds will raise their young for them. These kinds of birds are known as brood parasites. They’ve used this strategy for a long time, but we’re still learning about how they manage to succeed.

When a bird discovers a parasite egg in its nest, it either pushes it out or just raises that egg, too. The way a bird reacts to a parasite egg is dependent on other ecological factors, such as how populous the parasite species is.

The nesting bird’s reaction is an important part of the mafia hypothesis, which states that birds are more likely to raise parasite eggs if they fear retaliation from parasite birds.

The mafia hypothesis is expressed in this behavior: a cowbird lays an egg in another bird’s nest, and if that egg gets destroyed, they subsequently attack the nest and destroy the other eggs, forcing the birds to lay more eggs.

Once this happens, the host birds don’t kill further parasite eggs out of fear that their brood will be destroyed again.

A mathematical model developed by scientists from the Max Planck Institute for Evolutionary Biology found that this is the most common factor in determining how host birds react to parasite eggs.

If they have no reason to fear retaliation, say because there aren’t that many cowbirds around, they go ahead and push out that egg.

Other scientists question the hypothesis, though, because of a practice called farming, in which a parasite bird destroys a nest of eggs so that the hose has to lay a new clutch, and then sneaks one of its eggs in there.

Farming seems to require that the host bird not notice or not care about this new egg, though, and that doesn’t look very likely.

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Nature, Science

Why Are Swiss Stickelback Fish Evolving So Fast?

A population of stickleback fish is rapidly splitting into two distinct species in Switzerland’s Lake Constance.
A population of stickleback fish is rapidly splitting into two distinct species in Switzerland’s Lake Constance. Photo: EAWAG | David Alexander Marques.

There is a concept in evolutionary biology called sympatry, in which two interbreeding populations develop unique genetics and evolve into two species.

Sympatry is a rare biological event. Conventional biology has assumed that speciation only occurs when a mountain range or some other type of geographical or geological feature separates two populations. Increasingly though, sympatry has been gaining ground as more and more researchers seem to be finding it among their subjects.

Most recently, researchers in Switzerland have discovered that two populations of three-spined sticklebacks in Lake Constance and its watershed streams are evolving along these lines.

Basically, one group favors the streams, and another favors the lakes. They show marked differences in size and armor, which could be chalked up to lifestyle differences, but there are specific genetic differences between the two groups.

The most interesting part though, is that they not only both breed in the same streams, but also continue to interbreed. This clear example of sympatry could tell us quite a lot about evolution.

The general assumption is that evolution requires significant periods of time to occur. However, the three-spined stickleback has only lived in those waters for about 150 years, which is the blink of an eye compared to evolutionary timelines. This isn’t the first example of evolution on this kind of timescale though.

Apple maggots evolved in North America within two centuries of apples being first introduced to the continent. Cancers become resistant to drugs. Insects develop resistance to pesticides. Bacteria develop resistance to antibiotics.

A major factor contributing to this process may be the average lifespan of such organisms, but it doesn’t change the fact that we’re finding, more and more, that evolution is capable of a wide variety of timescales.

A group of customs agents in Hong Kong surround a large shipment of elephant tusks being confiscated as part of a concerted effort to stop international trade in ivory
Business, Sustainability, Wildlife & Animal Rights

Researchers Provide New Tools to Fight Illegal Ivory Trade

A group of customs agents in Hong Kong surround a large shipment of elephant tusks being confiscated as part of a concerted effort to stop international trade in ivory
Customs officers seize ivory tusks, rhino horn and leopard skins, with a street value of around €4 million, at the Hong Kong Customs and Excise headquarters in Hong Kong, China, 08 August 2013. Photo: International Fund for Animal Welfare | Flickr CC.

International efforts to shut down illegal ivory trade and to prevent the poaching of elephants or rhinos to create new products have failed. Ivory is still sold around the world and fetches high prices.

And thanks to the Internet, especially thanks to eBay, tracking down everyone who is buying or selling ivory is nearly impossible.

Determining what products are actually ivory, and which are illegal, takes time and effort, but there generally aren’t enough people working on the problem to keep up with traffic.

However, there is some cause for hope. Researchers at the University of Kent have developed a system, which scans Ebay listings and accurately determines if an item for sale is ivory or not. This search is possible despite most listings don’t use the term “ivory” to describe their illegal items.

This level of accuracy is about the same as a human investigator would provide, but the algorithm doesn’t yet utilize pictures. With further development the 93% success rate could be further increased. And to top it all off, the computer system is much faster than human investigators.

According to researchers at the University of Washington, most of those elephants are being killed in one of two places. The researches used DNA evidence taken from seized illegal ivory to make the determinations, and they learned a lot more about the illegal ivory trade as well.

This is good news for elephants and rhinos, and bad news for poachers. African elephants, of which there are less than 500,000, are being killed at a rate of about 50,000 per year. At this rate, that species is doomed.

Hopefully the international community can make use of this new information to not only put an end to ivory markets, but also prevent poachers from acquiring it in the first place.

Of course, convincing people that pointless decorations aren’t worth the life of endangered animals is the first step toward strangling the ivory market. Educating people about the complex social interactions between elephants is an important step towards increasing awareness of the problem. It’s also an important step toward protecting the world’s ecosystems.