Glaucis hirsutus (J.F.Gmelin, 1788)

Size and Weight

The rufous-breasted hermit (Glaucis hirsutus) averages 10.7 cm (4.2 in) long and weighs 7 g (0.25 oz) on average.

Bill Structure

Its bill is around 3.3 cm (1.3 in) long, strongly decurved, long and thin, and rather robust compared to the bills of other hummingbirds.

Plumage Coloration (Head and Torso)

This species has a brownish head, bronze-green upperparts, and rufous underparts.

Tail Feather Characteristics

Its tail has green central feathers and rufous outer feathers, and all tail feathers are tipped white.

Bill Coloration

The bill has a yellow lower mandible and a black upper mandible.

Sexual Dimorphism (Plumage)

The sexes are similar in appearance, but males have yellow streaking on the upper mandible, while females may have slightly duller plumage.

Sexual Dimorphism (Bill)

Female bills are also proportionally slightly shorter (a difference that is barely noticeable) and more decurved (a difference that is quite obvious when comparing individuals directly).

Male Appearance Comparison

Males are somewhat more distinct in appearance and resemble barbthroats (genus Threnetes).

Historical Taxonomic Misclassification

Males were once described as a separate species called the "black barbthroat" (T. grzimeki).

Invalid Subspecies Status

Similarly, the proposed subspecies abrawayae is based on individual variation in adult birds and is not taxonomically distinct.

Vocalization

The call of this species is a high-pitched sweet.

Habitat Preference

This hermit lives in forest undergrowth, often near running water.

General Diet

It feeds on nectar from a variety of understory flowers, as well as some small invertebrates.

Feeding Specialization

G. hirsutus has very discriminating feeding habits: it only visits flowers whose corolla length and curvature exactly matches the shape of its bill, while most other hummingbirds are much more flexible in the flowers they use.

Food Plant Diversity

Because of this, its food plants come from almost the entire diversity of angiosperms.

Preferred Zingiberales Food Plants

Zingiberales, such as Costus scaber (Costaceae), Heliconia standleyi, and Heliconia stricta (Heliconiaceae) are very popular food plants for this hummingbird.

Other Preferred Food Plant Orders

Other favored food plants include Gentianales such as Duroia hirsuta, Palicourea lasiantha, Psychotria bahiensis, and Psychotria platypoda (Rubiaceae), Lamiales such as Sanchezia peruviana (Acanthaceae) and Drymonia semicordata (Gesneriaceae), and Myrtales such as Cuphea melvilla (Lythraceae).

Feeding Avoidance Behavior

On the other hand, the hummingbird even avoids congeneric plants with flowers that have slightly different length and curvature.

Sexual Resource Partitioning Hypothesis

Given the difference in bill curvature between males and females, it is likely that the sexes avoid competing for the same food resource by visiting different plants, but little in-depth research has been done on this topic.

Coevolution Assessment

It is difficult to determine whether coevolution has occurred between this hummingbird and its food plants, but any coevolution that has happened is apparently less widespread than might be assumed.

General Pollination Context

Most plants visited by this hummingbird are also pollinated by less discriminating species.

Critical Pollinator Role

However, for some plants such as Cuphea melvilla, Psychotria bahiensis and P. platypoda, the rufous-breasted hermit appears to be a critically important pollinator.

Mutualism Conclusion

This shows that strong mutualisms between this bird and some of its food plants do exist, even though they are less common than the species' characteristic bill shape would suggest.