Dark-tailed laurel pigeon  (Columba bollii)

The dark-tailed laurel pigeon is classified as Near Threatened (NT) on the IUCN Red List (1). However, based on recent data collected by BirdLife International indicating that its range and population size are both increasing, this species is now thought to be Least Concern (LC) (4).

The dark-tailed laurel pigeon (Columba bollii) is a fairly small and relatively slim member of the pigeon family (Columbidae), although it can look rather plump when on the ground (2). German naturalist Carl Bolle was the first to distinguish this species from the laurel pigeon (Columba junoniae), and therefore it is also known as Bolle’s laurel pigeon (3).

The upperparts of the dark-tailed laurel pigeon are mostly a uniform dark blue-grey colour, except for a green and pink iridescent patch on the hind-neck and paler grey feathers on part of the tail. This species has a red bill with a powdery white cere, dull red feet, yellowish-white eyes and a reddish breast (2).

Juvenile dark-tailed laurel pigeons can be differentiated from the adults by their browner colouration and their buff-coloured wing-coverts (2).

This fairly shy species (2) has a mournful, hoarse cooing call (3) (4). Its territorial call has been described as a short ‘tru-tru-tru-tru-tru’, while its advertising call is ‘tru-tru-tru, tru-tru, tru-tr, tru’ (2).

The dark-tailed laurel pigeon is endemic to the Canary Islands of Spain, where it is found on Tenerife, La Palma, La Gomera and El Hierro. In the past, this species was very common, and was also thought to have occurred on Gran Canaria. However, due to clearance of its laurel forest habitat on these islands, the dark-tailed laurel pigeon has disappeared from many areas (4).

The dark-tailed laurel pigeon inhabits dense laurel forest in mountainous areas, and is often found in ravines and areas dominated by Azores laurel (Laurus azorica) and tilo (Ocotea foetens) (2) (4). It is also associated with fire tree (Myrica faya) and tree heath (Erica arborea), and is occasionally seen in more open, cultivated areas (4).

On Tenerife, the dark-tailed laurel pigeon is found at elevations of between 600 and 1,500 metres, although it prefers the higher elevations of 1,300 to 1,500 metres (2).

A frugivorous species (4), the dark-tailed laurel pigeon feeds principally on berries from the Azores laurel and tilo (2), although it is also known to eat grain and occasionally buds, leaves and shoots (4). Individuals of this species will gather in groups of 3 to 50 individuals (2) to feed on fruiting trees, generally plucking berries straight from the branches, but also feeding on the ground (2) (4). The dark-tailed laurel pigeon has been reported moving to lower elevations at times during the late summer, to take advantage of ripe cereals and fruit (4). It has also been observed feeding on cabbages and other crops in times of low berry availability (2).

The dark-tailed laurel pigeon is thought to breed throughout the year (5), but breeding usually occurs between January and September (4). The male performs breeding displays which include a series of deep bows (2). The female dark-tailed laurel pigeon produces two or three clutches of eggs a year, depending on the availability of food (2), with each clutch containing just one white egg (2) (3) which is incubated for 18 to 19 days (2). The nest is constructed of twigs and is always built in a tree (2) (3), often in the heaths Erica arborea (2) (5) or Erica scoparia, at heights of between 1.75 and 15 metres (2). The young of the dark-tailed laurel pigeon fledge between 30 and 35 days of age, and the young depend on the adults for some time after leaving the nest (2).

After taking off with a loud, clattering noise (3), the dark-tailed laurel pigeon has a low, fast flight (4), beating its wings regularly with an occasional sharp flick (3). However, it tends to stay within deep shade during the hottest part of the day (4). The dark-tailed laurel pigeon is territorial and will perform displays that include shallow, repeated ascents involving wing-clapping, followed by gliding down to a perch in a long, circular motion (2).

Historically, declines in the numbers of the dark-tailed laurel pigeon were a result of intensive exploitation of its laurel forest habitat. Despite a marked reduction in the extent of forest loss in recent years, habitat fragmentation still continues in some areas due to exploitation of wood for poles and tool handles, and habitat degradation occurs on La Gomera and El Hierro due to grazing pressure from sheep (4).

Illegal hunting and forest fires are moderate threats to the dark-tailed laurel pigeon, and human disturbance from recreational activities is also thought to occur during the breeding season.

Due to the dark-tailed laurel pigeon being a tree-nesting species, predation by introduced mammals is not as much of a problem as for ground-dwelling species (4). However, it still remains a threat, with the black rat (Rattus rattus) being a key culprit (5). Outbreaks of tuberculosis and Newcastle disease are also potential threats (4).

In 1996, a European Action Plan was published for the dark-tailed laurel pigeon, and regional or national law now protects the majority of areas inhabited by this species (4), including areas such as Garajonay National Park on La Gomera (2) (4). Hunting-free zones have been implemented, which coincide with reserves, but the restoration of pine forest is still awaiting full implementation (4). Between 2005 and 2008, a ‘LIFE’ project was carried out, funded by the European Commission, involving the eradication of exotic plants, the planting of native species, and raising public awareness surrounding the native forest-dwelling species of the islands (4). Some islands have rat control plans in place, while Tenerife aims to eradicate the non-native Monterey pine (Pinus radiata) and replace it with native species (4).

Further conservation measures proposed to ensure the future survival of the dark-tailed laurel pigeon include continued monitoring of its population and potential threats, protecting remaining laurel forests and establishing effective invasive species control plans. It will also be important to conduct awareness-raising campaigns. Fortunately, this species’ population currently appears to be stable, if not increasing (4).

More information on the dark-tailed laurel pigeon:

• BirdLife International - Dark-tailed laurel pigeon:
  http://www.birdlife.org/datazone/speciesfactsheet.php?id=2454