All About the American Redstart: Setophaga ruticilla
The American Redstart is a wood-warbler with the scientific name Setophaga ruticilla. Their order is passeriformes and their family is paulidae. As members of passeriformes, American Redstarts share characteristics with other passerines, though they are generally smaller than other passerines (Lozano et al., 1995). One such characteristic is the tendency for delayed maturation and its consequent effect on plumage maturation. Like other passerines, the plumage of adult and subadult, or young males are easily distinguishable. This difference in appearance has been studied in both the wild and in hand-raising circumstances. The results of such studies have indicated that subadult males oftentimes retain what appears to be a plumage similar in appearance to females, not attaining adult male plumage until approximately three molts later (Cucco and Malacarne, 2000).
Adult males have mostly black coloring with bright orange patches on the base of outer rectrices, remiges, and breast. Their underparts are white. Adult females (and subadult males) have a light gray head, a gray and olive back, and a whitish underpart, with light yellow patches on its tails, sides, and wings. Both males and females have long, flat bills and long expressive tails (“American Redstart”).
In addition to the differences in the appearances of subadult and adult males, young females also show differences in appearance from their older counterparts. While the older females show more yellow on their wings, it has been observed that subadult females show less yellow in these areas during the same time periods (Ficken and Ficken, 1967).
What are the social dynamics within American Redstart populations?
The social system and social dynamics of American Redstarts are in many ways centered around the existence and behavior of the adult males within the habitat. Much of the dynamics in play are regarding the relations between subadult and adult males. These interactions are based primarily on the subordinate status of the subadult males. Observation has shown that younger males both appear less imposing (female-like) and are more docile than their older counterparts. Older adult male American Redstarts are characteristically more aggressive, which is reflected in their aggressive defense of their territories. Due to this defense and the docile behavior of the younger males, the younger males obtain smaller territories at the periphery, while adult males’ habitats are clustered at the center of the region (Ickes and Ficken, 1970).
Interestingly, due to this aggressive behavior between subadult and adult redstarts, the similar appearance of females to the younger males results in initial aggressive behavior between adult males and females. This indicates that this specific plumage is associated with intraspecific aggression (Ickes and Ficken, 1970).
What is their breeding behavior?
As in many of passerine birds, observations and data have indicated that the reproductive success of male American Redstarts is directly related to age. It has been observed that adult males are drastically more successful than sub-adults at obtaining mates. One study’s results showed that in addition to being more successful at attracting mates, the female American Redstarts in fact showed a preference for adult male territories over sub-adult male territories (Lozano et al., 1995).
Male birds occasionally have more than one mate and brood at a time, while females have one. Courtship displays from the male American Redstarts include fluffing plumage, spreading its wings and tail, raising crown feathers, and bowing (Sherry et al., 2016).
Females pick where the nests will be, but males sometimes will show females potential sites as a way of courting them. What a female is specifically looking for in a nesting site has not been studied extensively, but it can be assumed that she will look for a site that has protection from predators through location or camouflage, a place that is stable and can withstand the elements, and a site where they can easily get materials to for nest building. These materials can include branches, bark strips, feathers, grass, pine needles, leaves, and other things that may be around the nesting site (Sherry et al., 2016).
After eggs are laid, the female will incubate them alone. During colder temperatures, the female spends more time incubating, so the male will occasionally feed the female so she won’t need to leave the eggs. A female will spend up to 85% of the daytime hours incubating the eggs. After the eggs hatch, both parents will feed the nestlings pretty evenly. The typically time of nesting is around 9 days but nestlings can be disturbed into leaving a day or two early, or may stay longer if they are only being taken care of by a widowed parent (Sherry et al., 2016).
Figure 4: ‘Adult male American Redstart feeding young.’
Figure 5: ‘Common Redstart Mating Pair’
Where are they found?
American Redstart birds have a great variety of habitats: willow and alder thickets, forests with both deciduous (trees that lose their leaves annually) and coniferous trees, as well as primarily coniferous forests (Ficken and Ficken, 1967). They will usually keep their nest in a maple, birch, or aspen tree. Generally, they breed in moist woodlands with abundant shrubs, often near water. During migration and nonbreeding periods, they prefer wooded areas or areas with shrubbery at low to medium elevations (Sherry et al., 2016).
What is their foraging behavior?
The American Redstarts eat mostly insects including: beetles, caterpillars, moths, leafhoppers, aphids, midges, crane flies, and small spiders or daddy longlegs. Along with insects, they eat some small seeds and berries. Males often like to fly higher than a female would to catch insects in the air then take them back to foliage. As expected, during certain times of the year, foraging patterns like flycatching or gleaning (the careful picking of food from the ground or tree surface) vary in usage. In Spring up until the beginning of May, flycatching has been observed to make up approximately eighty percent of American Redstart’s foraging behavior (Ficken and Ficken, 1967).
Watch video below to see a male American Redstart capture an insect in air (approximately 19 seconds).
Figure 7: ‘American Redstart: Foraging Behavior’
Cucco, M. and Malacarne, G. 2000. Delayed maturation in passerine birds: an examination of plumage effects and some indications of a related effect in song. Ethology Ecology and Evolution 3: 291-308.
Ficken, M.S. and Ficken, R.W. 1967. Age-specific differences in the breeding behavior and ecology of the American Redstart. The Wilson Bulletin 2: 188-199.
Ickes, R.A. and Ficken, M.S. 1970. An investigation of territorial behavior in the American Redstart utilizing recorded songs. The Wilson Bulletin 2: 167-176.
Lozano, G.A., Perreault, S. and Lemon, R.E. 1995. Age, arrival date and reproductive success of male American Redstarts Setophaga ruticilla. Journal of Avian Biology 2: 164-170.
Sherry, T.W., Holmes R.T, Pyle P., and Patten M.A. 2016. American redstart. Birds of North America Online.
Figure 1: Trimble, Jeremiah. American Redstart Setophaga ruticilla: ML38206751. October 22, 2016. Macaulay Library Online. Accessed: April 27, 2018. https://macaulaylibrary.org/asset/38206751.
Figure 2: Lipton, Evan. American Redstart Setophaga ruticulla: ML28948631. May 17, 2016. Macaulay Library Online. Accessed: April 27, 2018. https://macaulaylibrary.org/asset/28948631.
Figure 3: Gauthier, Yves. American Redstart Setophaga ruticulla: ML59224231. May 24, 2017. Macaulay Library Online. Accessed: April 27, 2018. https://macaulaylibrary.org/asset/59224231.
Figure 4: Andree, Dan W. Adult Male American redstart feeding young. August 16, 2014. Youtube. Accessed: April 27, 2018. https://youtu.be/3Ej1l4lFnx8.
Figure 5: Littleicecage. Common Redstart Mating Pair. May 6, 2013. Youtube. Accessed: April 27, 2018. https://www.youtube.com/watch?v=eOZ9k-anOBw.
Figure 6: Distribution of the American Redstart. Birds of North America (online). Accessed: April 27, 2018. https://birdsna.org/Species-Account/bna/species/amered/distribution.
Figure 7: Barrentine, Carl. American Redstart: Foraging Behavior. May 28, 2015. Youtube. Accessed: April 27, 2018. https://www.youtube.com/watch?v=9Fp-tOfpJlg.