The Blue Dacnis (Dacnis cayana) is a wide spread and common member of the Neotropical avifauna. Like other members of the genus, they are small active canopy dwelling tanagers with distinctive short pointed bills. They are sexually dimorphic, with the males brilliant turquoise and black, while the females are green with powder bluish heads; this dichromatism is believed to be due to differences in feather structure (Barreira 2008).
The Blue Dacnis is widespread and common in the tropical lowlands from Honduras to Paraguay, with bright turquoise and black males and green females. As such, similar species vary depending on geographic locality and sex. The adult male Blue Dacnis is most likely to be confused with adult male congeners. It is perhaps most difficult to discriminate from the Black-legged Dacnis (D. nigripes), where these two species co-occur in the coastal forests of southeastern Brazil. The Blue Dacnis is best identified from the Black-legged Dacnis by having pinkish legs and more colorful females, whereas the Black-legged Dacnis has black legs, less black on the throat and mantle, a smaller and thinner bill, and relatively drab females (Isler and Isler 1987, Sick 1993). All other similar looking male Dacnis species have dark legs and yellow eyes, and all similarly colored male Cyanerpes honeycreepers have longer and more decurved bills (Ridgely and Greenfield 2001, Schulenberg et al. 2007). The female Blue Dacnis is more distinct in the genus, being brighter green with blue on the cap and auriculars and on the upper wing coverts at the bend of the wing. She is perhaps more likely to be confused with the female Capped Conebill (Conirostrum albifrons) and female Chestnut-vented Conebill (C. speciosum), both of which have green on the body and blue heads (Hilty et al. 2003, Restall et al. 2007). The female Capped Conebill has a gray nape, instead of green, and the female Chestnut-vented Conebill is dull white ventrally, whereas the female Blue Dacnis is green below (Hilty 2011).
This description is for Dacnis cayana cayana. For other subspecies see geographic distribution.
Blue Dacnis (Dacnis cayana) are a small dacnis, with a thin and pointed dusky grey bill. The adult males of this species have black lores that extend around the eyes to form a black mask that ends behind the eye in a thin point, and a narrow central throat patch that is also black (Hilty 2011). The rest of the head and nape are a bright turquoise-blue (Hilty 2011). The mantle and back of the Blue Dacnis are black, narrowing to a point just above the rump (Hilty 2011). The tail is black, with some of the outer feathers edged blue (Hilty 2011). The upper wing and coverts are black, with the median coverts being narrowly tipped blue, and the greater coverts, primary coverts, flight feathers, and tertials being prominently edged with blue (Hilty 2011). The underside of the male Blue Dacnis is turquoise, from chest to undertail coverts (Hilty 2011).
The adult females of this species are primarily bright leaf green, with a grayish throat, some blue on the shoulder, and a bluish or bluish-violet head. Older females range from yellowish green to brilliant green (Restall et al. 2007). The coverts, primaries and tail feathers are black, with extensive green edges.
The immature males are colored similarly to the females, but have a mask and bib. They also have a mantle that is slightly dusky (Restall et al. 2007). The juvenile is colored similarly to the female, but the blue on the head is more restricted and the underparts are more yellowish. The juveniles will also have a darker mask than the female (Restall et al. 2007).
Tanagers have either a complex basic strategy or a complex alternative strategy (Ryder and Wolfe 2009). According to Isler and Isler (1987) most tanagers only molt once a year, with the prebasic molt occurring after breeding season (Isler and Isler 1987, Ryder and Wolfe 2009). The juvenile and immature plumages of the Blue Dacnis are described in Restall et al. (2007), but more specific information on molt and timing are not available.
Bill: The Blue Dacnis have a pointed bill that is purplish black (Restall et al. 2007).
Information needed. Contribute
Iris: The iris of the Blue Dacnis is red (Ridgely and Greenfield 2001).
Legs: The Blue Dacnis has pink legs (Restall et al. 2007).