Beaks Shed Light on Why Closely-Related Bird Species Cannot Coexist

Closely-related birds of the same species cannot coexist as they are ecologically similar and will out-compete each other, says a new study.

Researchers from Oxford University, U.K., studied the closely-related species of the ovenbird family from South America. Ovenbirds are found living in different habitats, from deserts and grasslands to tropical forests.

Ovenbirds get their name for the nest they build. They build nests that resemble a traditional baking oven. These birds have diverse beaks that are used as a tool to consume food items. Some birds have evolved with unusual-looking long curved bills, in order to extract insects from bamboo stems or beneath the bark of trees.

For their study, the research team compared the records giving details on when the birds diverged and their habitat where they stay today. They found that the birds that separated long ago and evolved with different beaks are able to coexist after they became two separate species.

But, ovenbirds that moved to new habitats due to climate change might not be able to survive because a closely-related species already living there would out-compete them for resources, said the researchers.   

"Competitive exclusion between species is generally thought to be limited to relatively small spatial scales, such as between individual birds or across local patches of habitat," lead author of the study Alex Pigot, of Oxford University's Department of Zoology, said in a statement.

"In our work we are able to show that competition is a major factor responsible for excluding closely-related species from entire regions. The key was being able to rule out other explanations like geographical barriers, such as rivers, or unsuitable habitats from being the main barriers to 'sister' species co-existing," he said.

Researchers noticed that those birds that have been able to evolve different beaks have been able to survive in any place. They suggest it will take a longer time for birds to evolve different foraging niches which will allow them to coexist with their close relatives.

Some birds get displaced to newer locations when the temperature becomes hot or dry due to climate change. The area of new habitats might be smaller than the current estimation, as related species of the birds might have occupied the region and will out-compete any newcomers.

Researchers point out that the impact of climate change on ovenbirds could not be understood without considering the competitive interaction between species.

The findings of the study are published in the journal Ecology Letters.