The belted kingfisher (Megaceryle alcyon) is a medium-sized bird found across North America. It gets its name from the prominent blue-gray band found across the breast of adult females. This striking band distinguishes the female belted kingfisher from the male, which has a more subdued plumage of blue-gray on the head, wings and back with a white underside. The brighter plumage of the female belted kingfisher raises an interesting question – why are females of this species more colorful than males?
In most bird species, it is the male that sports more colorful and decorative plumage. This is because males must compete to attract mates and their bright colors help catch the eyes of females. Females, who do most of the work of nesting and raising young, tend to have more camouflaged plumage to help hide them from predators. So why does this pattern reverse in belted kingfishers? Keep reading to learn more about some of the leading hypotheses that may explain the belted kingfisher’s peculiar reversed sexual dimorphism.
Hypothesis 1: Female Defense of Nesting Territory
One major hypothesis for why female belted kingfishers are more colorful is related to their nesting habits. Belted kingfishers nest in burrows along the banks of rivers, lakes and estuaries. The female is solely responsible for excavating these burrows, which can take up to three weeks to dig and can extend up to 8 feet into the ground! She must work hard to defend this nesting territory from intruders during the breeding season.
Displaying bright plumage could help signal to trespassing belted kingfishers that this territory is occupied. The striking blue band and reddish belly of the female acts as a visual warning to indicate her ownership of the nest site. Drabber males, who do not need to establish breeding territories, do not need such flashy plumage. So the female’s colorful appearance helps ward off competitors from her breeding grounds.
Table 1. Roles of Male and Female Belted Kingfishers During Breeding Season
Sex | Roles |
---|---|
Female | – Excavates nesting burrow in riverbank – Lays and incubates eggs – Broods and feeds hatchlings – Defends nesting territory |
Male | – Guards female and assists with defense – Delivers food to female and chicks |
Hypothesis 2: Camouflage While Hunting
Another related hypothesis involves the division of labor between male and female belted kingfishers after eggs hatch. While the female stays busy feeding and defending the chicks in the nest burrow, the male takes over the crucial job of catching fish to provide food.
Male belted kingfishers must hunt while perched along river banks and shorelines, waiting for the opportunity to dive down and catch fish and aquatic invertebrates in their large bills. Their plumage of grayish-blue feathers provides ideal camouflage against the rocks and water while they are waiting stealthily for prey.
A bright blue breast band could scare away fish and make males more obvious to prey while hunting. So the duller male plumage helps provide an advantage in catching food to feed their hungry broods. On the other hand, the showy colors of the female help her stand out boldly to defend her turf rather than hide.
Table 2. Foraging Techniques of Male vs. Female Belted Kingfishers
Sex | Foraging Strategy |
---|---|
Male | – Perches inconspicuously along shorelines – Ambushes prey by diving from perch |
Female | – Hovers above water – Plunges directly down to capture prey |
Hypothesis 3: Signaling Experience and Quality
The bright plumage of female belted kingfishers could also signal their overall quality as a mate. Studies have shown that the intensity of the rusty band on her belly correlates with her body mass and condition. Females who have successfully nested and raised chicks in the past may display brighter plumage.
In contrast, younger females just starting out display duller bands until they gain experience. Males likely prefer more vibrant females since it indicates she has successfully reproduced before and knows how to adequately care for eggs and offspring. The bright plumage signals her overall breeding expertise and that she would make an ideal mate and co-parent.
Table 3. Plumage Indicators of Female Quality and Experience
Female Plumage | Indicated Quality |
---|---|
Brighter blue breast band | Higher body condition |
More intense rusty belly | More experience nesting and raising young |
Duller colors | Younger, less experienced female |
Conclusion
In summary, the brighter plumage displayed by female belted kingfishers likely serves several important functions related to their mating and parental duties. The showy blue band helps defend critical nesting sites, while their rusty bellies signal experience and body condition. Meanwhile, the duller male plumage provides better camouflage while hunting to provide food for their offspring. So the reversed sexual dimorphism in this species has evolved to support the specialized roles of each sex in reproduction. Understanding differences in male and female appearance and behavior offers insights into the unique breeding ecology of belted kingfishers.