Endangered pigeon tricked by coos

Pink Pigeon has recovered from a low of just nine individuals to 400, but now appears not to be able to increase further. Photo: Andrew Wolfenden.
Pink Pigeon has recovered from a low of just nine individuals to 400, but now appears not to be able to increase further. Photo: Andrew Wolfenden.
Efforts to save the critically endangered Pink Pigeon could be hampered by ‘signal jamming’ coos that trick them into thinking they are surrounded by rivals.

Calls from an invasive bird species could be inadvertently stopping the rare Pink Pigeon’s population from increasing by tiring the species out, new research from Manchester Metropolitan University (MMU) suggests.

Pink Pigeon is only found on the tropical island of Mauritius, famous for its iconic extinct relative, Dodo. It was brought back from the brink of extinction and has recovered from a population of just nine in 1990 to approximately 400 in 2013. However, the species remains endangered despite decades of conservation effort by the Mauritian Wildlife Foundation (MWF).

Now a study has shown that the pigeons cannot discriminate between its own calls and those from its congeneric sister species, Malagasy Turtle Dove, as its coos are jammed much like an army disrupting an enemy’s radio communications. It is thought that Malagasy Turtle Dove was brought to Mauritius in the late 1700s by trading ships, and is thus an invasive species.

Malagasy Turtle Dove has calls similar enough to Pink Pigeon to effectively interfere with the rare species's communication. Photo: Andrew Wolfenden.

Pink Pigeon's range is restricted to the Black Gorge NP on the south coast of the 1,270 square-mile island, and it is not fully clear why the species fails to recolonise the rest of the island.

By playing pre-recorded coos through remote controlled speakers and analysing the pigeon’s response for his MSc project, MMU researcher Andrew Wolfenden provided the MWF with a possible answer as to why the pigeons do not thrive.

Signal jamming – when calls from two species are similar and individuals mistakenly respond to the wrong species – may be leading pink pigeons to believe they are surrounded by a greater number of rivals than is actually the case. As pigeons use their coos for attracting mates and repelling rivals, when Pink Pigeons respond to the dove’s call they are likely to waste both time and energy. This will have a negative impact on their breeding success and potentially restrict opportunities to establish a territory, which they wrongly believe to be occupied by rivals.

Andrew said: “Pink Pigeon is the last remaining endemic pigeon species on Mauritius after the demise of Dodo and Blue Pigeon. Intensive conservation schemes helped the population to grow but efforts to encourage the bird to establish new habitats have failed and it is unclear why.

“Signal jamming could be causing this by confusing the pigeons, possibly having a series of knock-on effects. Hopefully these results will contribute to safeguarding the species on Mauritius.”

Wolfenden, A, Jones, C G, Tatayah, V, Züel, N, and de Kort, S R. "Endangered pink pigeons treat calls of the ubiquitous Madagascan turtle dove as conspecific." Animal Behaviour 99: 83-88. doi:10.1016/j.anbehav.2014.10.023.