A critically endangered bird species called the São Tomé grosbeak is the world’s largest canary, 50% heavier than the next largest species, according to a new study published in the journal Ibis.
The São Tomé grosbeak, endemic to the island of São Tomé in the West African Gulf of Guinea, is one of the least known birds in the world.
This bird was discovered in 1888 by the Portuguese naturalist Francisco Newton, who collected a male in the forests of south-eastern São Tomé; in 1890, Newton collected another two males in the south-western forests.
After years of eluding ornithologists, the species was feared to be extinct.
But in August 1991, a group of researchers spotted several birds in the remote forests in the south-west of the island.
Until now, the São Tomé grosbeak has been categorized as Nesospiza (the new finch). But new DNA analyses, performed by Dr. Martim Melo of the Universities of Porto and Cape Town and co-authors, show that the species is actually an ‘Old World finch within the Crithagra seedeater/canary group.’
“Our molecular data confirmed, with strong statistical support from all inference methods and datasets used, that the São Tomé grosbeak is an Old World finch — the most widely proposed taxonomic position — rather than a weaver,” the researchers said.
“The São Tomé grosbeak (Crithagra concolor) is an island giant.”
“It is by far the largest canary in the world, 50% heavier than the thick-billed seedeater (Crithagra burtoni), until now considered the largest species in the group.”
“The gigantism of the São Tomé grosbeak is striking when its morphometrics are compared with those of its partially sympatric sister species, the Principe seedeater (Crithagra rufobrunnea).”
Dr. Melo and his colleagues added: “although the Principe seedeater is the fourth largest Crithagra in the world, grosbeak males had a body mass which was double that of seedeater males, and a bill depth that was almost double (93% larger), with bill length and width 44% and 48% greater, respectively.”
“The divergence between the São Tomé grosbeak and the Principe seedeater took place around 1 million years ago, which coincides with one of the most active volcanic periods of the 13-million-year-old São Tomé island,” they said.
Martim Melo et al. 2017. The endangered São Tomé Grosbeak Neospiza concolor is the world’s largest canary. Ibis 159 (3): 673-679; doi: 10.1111/ibi.12466