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Version 1.0

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Sunbittern Eurypyga helias

Sarah A. MacLean
Version: 1.0 — Published July 1, 2010



Nest: A globular structure composed of decayed leaves, sticks, and green moss (Stiles and Skutch 1989) held together predominately by mud (Lyon and Fogden 1989, Bartlett 1866, Thomas and Strahl 1990). Nests can be lined with green leaves (Stiles and Skutch 1989), or not lined at all (Thomas and Strahl 1990).

Table 1 - Sunbittern nests in Venezuela, from Thomas and Strahl 1990

Year and Nest#

Nest Tree SpeciesNest tree height (m)Nest height (m)Nest tree dbh (cm)Nest branch diameter (cm)Nest diameter (cm) outside Nest diameter (cm) cup Nest depth (cm) outside Nest depth (cm) cup 
1Sclerobium aureum 9.5  3.3  22 13.5  23 x 17  13 x 13  5.5-6 3.0 
2Guazuma ulmifolia 7.9 3.9 16  8.0  24 x 16  13 x 12  5.4-6  3.2 
3 Guazuma ulmifolia  11.4 5.1 23 - - - - -
4Randia venezuelensis 3.9 2.0 10 5.5 22 x 15 13 x 13  7.0 3.1
5Zanthoxylum cuantrillo 7.2 3.5 14 6.5  21 x 17 13 x 13 5.3 2.9
6 Acacia articulata 4.1  1.3 5 5.0 21 x 15 12 x 11 7.0 2.5
7Guazuma umifolia 4.3  2.2 12 6.9 19 x 17 13 x 12 6.0 2.1
8 Guazuma umifolia 4.8  2.7 18 7.2 22 x 18  14 x 13 6.5 3.2
9 Sclerobium aureum same  as 1     21 x 16 13 x 12 6.2 3.0
10Guazuma umifolia  same  as 3    - - - -
11 Pterocarpus acapulcensis 12.9 7.2 73 - - - -  -

Sunbittern on a nest, Plantation Trail, Panama Canal, Panama; April 2008 © Joel N. Rosenthal Nests are built on on bare branches in open areas (Thomas and Strahl 1990), usually near streams but not directly above water (Skutch 1947). When nests are built at an angle, they are constructed to be deeper on one side so that the cup is level (Thomas and Strahl 1990). May also nest on the ground (Dubs 1992). Both sexes are involved in nest construction (Stiles and Skutch 1989).

Eggs: Laid March-June in Costa Rica (Stiles and Skutch 1989), but possibly as early as May or as late as August in Suriname (Heverschmidt 1968). Bartlett (1866) documented a captive pair which laid a second clutch in August. The exact lay date is probably variable and influenced by seasonal rains because of the reduced availability of food for chicks and mud for nest construction (Thomas and Strahl 1990). Wild birds lay a clutch size of two to three, while captive birds tend to lay only one egg (Lyon and Fogden 1989). Color is pale pinkish-cinnamon (Haverschmidt 1968) to yellowish-brown, with irregular blotches of reddish brown and grayish lilac (Dubs 1992).

Measurements of three eggs (from Thomas and Strahl 1990): 41.7 x 33.1 mm, 26.0 g, 11 days before hatching; 43.3 x 34.4 mm, 25.3 g, 9 days before hatching; 39.6 x 32.5 mm, 20.7 g, 1 day before hatching.

Incubation: Incubation period is 27 days (Bartlett 1866). Both parents share incubation duty, with each adult sitting on the nest continuously for two-day intervals during the first half of incubation, then in one day-intervals during the last 12 days of incubation. Parents switch places only during the morning. Incubating birds will occasionally get up to turn the eggs over, displaying a characteristic tail-swaying behavior (Lyon and Fogden 1989).

Sunbittern chick in the San Diego Zoo; 16 April 2009 © Lianne TauxeChick development: Hatch asynchronously, with a downy covering and open eyes. Plumage is light brown, with black marbling down the head and neck. Nestlings do not appear to compete aggressively for food, despite size differences that can become dramatic as development progresses. Parents may attempt to feed shells to chicks after washing them in the nearby river. Chicks defecate over the edge of the nest throughout the nestling period (Lyon and Fogden 1989).

Day 1-3: Some difficulty standing (Lyon and Fogden 1989), unable to hold head up for more than 15 sec. Fed primarily by regurgitation (Thomas and Strahl 1990).

Day 4-5: Capable of eating large prey such as frogs and lizards (Lyon and Fogden 1989, Thomas and Strahl 1990).

Day 7-10: Capable of standing and flapping wings. Size differences are very apparent. Chicks begin to show characteristic tail-waving behavior (Lyon and Fogden 1989, Thomas and Strahl 1990). Chicks begin practicing the Frontal Display. Also capable of trilling and answering adult trills (Thomas and Strahl 1990).

Day 12: Primaries/secondaries emerge 2 cm beyond sheaths, larger chick is twice the size of the smaller one (Lyon and Fogden 1989). Frontal Display has become fully developed (Thomas and Strahl 1990).

Day 18: Natal down begins to be lost on the head and neck, being replaced by adult-like contour feathers (Thomas and Strahl 1990).

Day 17-24: Fledging (some possibly premature) at well below adult weight (Thomas and Strahl 1990).

By two months, the young bird is indistinguishable from its parents (Bartlett 1866).

Parental attendance: Chicks are attended almost continuously during the first week after hatching, after which attendance drops until the fourth week, at which point chicks are unattended most of the time. The attending parent will often greet its returning partner by bobbing its head up and down, or less frequently with a begging display similar to that of the of the chicks. One parent, probably the female, tends to be more attentive to the chicks. The other may give a broken wing display if a threat approaches the nest (Lyon and Fogden 1989). Parents stay within vocal contact of each other and remain within 100 m of the nest (Thomas and Strahl 1990). If a second clutch is laid, the male becomes the more attentive incubator while the female continues to feed the chicks from the first clutch (Bartlett 1866). During the last few days of tending nestlings, one parent may leave the nest and cease care of the chicks, most likely as a strategy to make the nest less conspicuous (Thomas and Strahl 1990).

Food: Chicks may gape, emitting a high-pitched peeping, to receive regurgitated food (Thomas and Strahl 1990), or may simply peck food items out of the beak of the parent without begging (Bartlett 1866, Lyon and Fogden 1989). Dobsonfly larvae makes up a large proportion of the food given to chicks, with other significant sources being frogs, tadpoles, and crabs (which are not brought to the nest intact). Prey items that are taken whole from the beak of the parent are often washed by parents beforehand, perhaps to remove bitter secretions. If food items are rejected, parents will wash them before offering them again (Lyon and Fogden 1989).

Recommended Citation

MacLean, S. A. (2010). Sunbittern (Eurypyga helias), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/nb.sunbit1.01