One of the world's most critically endangered birds, Kenya's taita apalis (Apalis fuscigularis), has suddenly and inexplicably become much, much rarer, according to BirdLife International.

The organization, which has funded research into the species through its Preventing Extinctions Program, says that field work conducted in 2009 and 2010 found almost no taita apalis remaining in Kenya's forests. With sightings of the bird down nearly 80 percent compared with 2001, BirdLife now estimates the species's population at somewhere between 60 and 130 individuals. Previous estimates from just nine years ago placed the population at between 300 and 650 birds.

According to BirdLife, there is no obvious reason for this decline, as the birds' habitat, the Ngangao Forest, has "little to no illegal logging," and no other potential threats are immediately apparent. Previous research into the species, however, published April 26 in the journal Bird Conservation International, called the one of the three patches of forest where the taita apalis lives "highly degraded." BirdLife did not find any of the birds in that particular stretch of forest.

Photo by Lawrence Wagura, courtesy of BirdLife International