3 July 2012

Black and blue

The Black-legged Dacnis is a rare and highly sought-after endemic of Brazil's Atlantic Forest. Described in 1989 by Ridgely and Tudor as "rarely seen", they remain very erratic in their appearances, with Intervales State Park in São Paulo State being about the only reasonably reliable site. At REGUA, in Rio de Janeiro State, Black-legged Dacnis was until recently, recorded only very rarely. Then in March 2009, a pair with young turned up at the wetland and since then very small numbers have occurred annually here between January and May.

By June the dacnises have usually gone, but this year many of the trees around the wetland have been fruiting simultaneously, attracting large numbers of birds. Social Flycatcher and Tropical Kingbird were the most numerous species, but also present were lots of Blue Dacnis, Swallow Tanager and exceptional numbers of Black-legged Dacnis, with perhaps as many as 20 or even 30 present, including flocks of up to 13 birds. Other notable species attracted to the fruit included small numbers of Blue Ground-Dove, Blue-winged Parrotlet, Planalto Tyrannulet, Bananaquit, Red-legged Honeycreeper and Fawn-breasted Tanager.

Adult male Black-legged Dacnis, REGUA wetland, 11 June 2012.

Severe loss of lowland humid Atlantic Forest is the main threat to the Black-legged Dacnis, but their rarity also makes them a target for the cage-bird trade. Until recently they were classified as Vulnerable by BirdLife International, however, similarity with the common and widespread Blue Dacnis may have led to them being under recorded, and so in 2004 their status was revised to Near Threatened. Last month, adult males, adult females and immatures males were all present at REGUA, allowing excellent opportunities to compare side by side with Blue Dacnis.

Male Black-legged Dacnis, REGUA, 11 June 2012. Very similar to male Blue
Dacnis but slightly smaller with a less extensive black throat 'bib', more blue on the
scapulars and wing coverts (note the lack of black around the carpal), blackish
rather than reddish legs, and a noticeably shorter bill.

Male Blue Dacnis, REGUA, 10 June 2012. Note the larger black throat 'bib', the
black centres to the wing coverts, black alula (and around the carpal), reddish
legs and longer bill.

Female Black-legged Dacnis, REGUA, 11 June 2012. Dull brownish-olive above
with a blue-grey on the flight feathers, rump, crown and ear coverts, and
creamy-buff below. They also hate being photographed, hence the rubbish photo!

Female Blue Dacnis, REGUA, 16 June 2012. Female
Blue Dacnis are easy to identify, being green all
over with blue on the crown, forehead and ear
coverts, and are complete posers.

Black-legged Dacnis breed between mid October to mid February and nests have been found in secondary forest1. Immature birds are often seen at REGUA, which suggests that Black-legged Dacnis breed very close to, if not actually on the Reserve. This year several immature males were present accompanied by both adult males and females.

Immature male Black-legged Dacnis, 13 June 2012. Superficially similar to a female
but with grey rather than buff underparts, more blue on the head and wing
coverts, patchy black throat and black lores.

Both Blue and Black-legged Dacnis have a similar diets of fruit, seeds, insects and nectar (both also visit fruit feeders). Black-legged Dacnis have been observed feeding together on nectar1, but last month at the REGUA wetland I observed both species feeding together on Trema micrantha and Miconia fruits, along with the occasional Red-legged Honeycreeper.

Black-legged Dacnis, REGUA, 11 June 2012. This bird was feeding with the
Blue Dacnis below.

Blue Dacnis, REGUA, 11 June 2012 feeding on Trema micrantha berries.

Trema micrantha are a pioneer tree species that has been planted in adundance around the wetland. They grow well in open areas and help develop a nutrient rich soil layer that successive interior forest tree species require. The clumps of small orange-red to yellow berries grow on thin vertical branches, and I observed Black-legged Dacnis, Blue Dacnis and Red-legged Honeycreeper all adopting the same feeding technique - reaching downwards from the top of the branch, often hanging upside down.

Black-legged Dacnis, REGUA, 11 June 2012
feeding on Trema micrantha berries.

Female Red-legged Honeycreeper, REGUA, 11 June
2012. One of only a few Neotropical passerines to
have an eclipse plumage.

The annual occurrences of Black-legged Dacnis at REGUA in recent years is a testament to the success of Reserve's reforestation programme. Planted between 2006 and 2008, the young forest around the wetland is already providing an important food source for many birds. The shear abundance of fruit last month also attracted a large influx of Swallow Tanager - a nomadic species usually only found at REGUA in any numbers between January and March - with at least 60 birds present. They were often seen feeding and resting with Black-legged Dacnis, so maybe Black-legged Dacnis and Swallow Tanager move around together searching for food sources? Perhaps this explains the unusually large numbers of Black-legged Dacnis around at REGUA last month?

References

1 Whittaker, A., Parrini, R., & Zimmer, K.J. 2010. First nesting records of the Black-legged Dacnis Dacnis nigripes, with notes on field identification, ecology, conservation and recent records from Espírito Santo, Brazil. Cotinga 32): 65–73.

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