Bohemian Waxwings (Bombycilla garrulus) and Cedar Waxwings (Bombycilla cedrorum) are two closely related species of waxwing birds found in North America. Both are highly social birds that form large nomadic flocks, especially in winter. This raises the question – do these two waxwing species ever flock together?
Bohemian Waxwing Overview
The Bohemian Waxwing is a medium-sized songbird, measuring about 20–24 cm (7.9–9.4 in) in length with a wingspan of 34–40 cm (13–16 in) and weighing 58–72 g (2.0–2.5 oz).
Some key identification features include:
– Grayish-brown overall plumage with subtle peach undertones. Black mask and chin. White and yellow undertail coverts.
– Pointed crest. Short black bill. Black eyes.
– Bright yellow and white wingtips formed by wax-like secondaries. Red wax-like tips on some tail feathers.
– Juveniles are streaked and lack waxy wingtips.
Range and Habitat
The breeding range of the Bohemian Waxwing is in northern Eurasia, from Scandinavia through Russia.
In North America, Bohemian Waxwings are only found in Alaska and northern Canada during the breeding season. They nest in open coniferous forests.
In winter, Bohemian Waxwings can irregularly irrupt south into the northern United States and more rarely as far south as California, Texas, and Georgia. These winter movements are tied to food availability.
Bohemian Waxwings prefer older fruiting trees and shrubs, especially those bearing berries and small fruits. They often wander nomadically in search of food sources.
Diet
The diet of Bohemian Waxwings is composed primarily of fruits and berries. Foods eaten include:
– Mountain ash, rowan, and other ornamental crabapples or fruit trees
– Hawthorn and other shrubs with persistent winter fruits
– Juniper and cedar berries
– Serviceberries
– Buckthorn berries
– Fruits of viburnum, dogwood, and sumac
Bohemian Waxwings will also occasionally eat insects, especially in summer. They capture flying insects on the wing.
Social Behavior
Bohemian Waxwings are highly gregarious, social birds. They form large nomadic flocks that wander irregularly in search of fruit sources. Flock sizes can range from just a few dozen birds up to several hundred.
Social behaviors include:
– Flocking, with coordinated movements and constant contact calls between birds to maintain cohesion.
– Communal roosting in dense trees and shrubs.
– Social feeding in loose aggregations, often passing fruits to each other.
– Resting in close proximity to preen and sun themselves.
These social bonds are maintained year-round. Pairs may isolate briefly for breeding but otherwise Bohemian Waxwings move and act as a flock.
Cedar Waxwing Overview
The Cedar Waxwing is a close North American relative of the Bohemian Waxwing, also medium-sized at about 18–20 cm (7.1–7.9 in) in length with a 31–34 cm (12–13 in) wingspan and weighing roughly 30 g (1.1 oz).
Some identification features include:
– Smooth gray-brown plumage. Yellow undertail coverts. Black mask with white borders. Small crest.
– Tail tip is yellow, unlike the Bohemian’s red tail tip.
– Wings have vivid red wax-like tips on secondary feathers. Juveniles lack these tips.
– Short yellow tail band. Yellow belly. Yellow forewings.
Range and Habitat
Cedar Waxwings are native breeding birds throughout most of North America. They nest in open woodlands, forest edges, and hedgerows.
In winter they may wander nomadically but do not make major migrations. Their range extends south to Central America.
Like Bohemian Waxwings, they favor fruiting trees and shrubs. They are especially tied to cedars and junipers which provide winter berries.
Diet
The diet of Cedar Waxwings consists primarily of fruits and berries including:
– Serviceberries, juniper berries, dogwood, sumac, and mistletoe berries.
– Ornamental crabapples, hawthorns, and pyracantha fruits.
– Raspberries, mulberries, and strawberries.
– Band-tailed pigeon cherries.
They will also occasionally eat insects, especially winged ants which are caught in flight.
Social Behavior
Like Bohemian Waxwings, Cedar Waxwings are highly social, nomadic flocking birds. They gather in large flocks from just a dozen to over 100 birds that travel together while foraging.
Behaviors promoting social bonds include:
– Constant contact calls between flock members to coordinate movements.
– Sharing of fruits by passing them from bird to bird.
– Preening each other to strengthen social ties.
– Roosting communally in dense trees and shrubs.
Breeding pairs may break away briefly but otherwise Cedar Waxwings remain highly social and nomadic year-round, traveling in flocks between food sources.
Do Bohemian and Cedar Waxwings Flock Together?
The Bohemian Waxwing and Cedar Waxwing share very similar behaviors, habitats, diets, and lifestyles. Given their highly gregarious natures, do flocks of these two species ever mix in the parts of North America where they overlap?
The answer is occasionally, but rarely. When their ranges do overlap, the following interactions occur:
Winter Range Overlap
In winter, Bohemian Waxwings can irregularly move south into Canada and the northernmost U.S. states. Here, their range overlaps with that of Cedar Waxwings.
However, Bohemian Waxwings tend to wander less predictably compared to Cedar Waxwings. They seek out specific fruit sources like mountain ash and ornamental crabapples, compared to Cedars which use a wider variety of winter-persistent fruits.
So while both species may occur in the same general regions in winter, Bohemians are less likely to flock with Cedars. Their food needs and nomadic habits differ slightly.
Occasional Mixed Flocking
There are occasional reports of Bohemian and Cedar waxwings mixing together into temporary multi-species flocks, especially when feeding communally on an abundant food source.
For example, both species often gorge on introduced European mountain ash berries. If these trees are fruiting heavily, loose flocks may mix.
Courtship displays and social behaviors like preening have also very rarely been observed crossing between Bohemian and Cedar flocks. This suggests some limited social interchange.
However, these mixed flocks appear to be temporary. More systematic studies show the two species flocking separately most of the time. Stronger social ties exist within each species.
Differences in Breeding Range
Another factor limiting flocking is that Bohemian and Cedar Waxwings segregate during the breeding season.
Bohemians nest far to the north in Alaska and Canada, while Cedars nest widely across the continental U.S. and southern Canada. So opportunities for mixed flocks are reduced while breeding.
Habitat Differences
Finally, habitat preferences differ slightly between the species in a way that reduces co-occurrence outside of winter.
Cedar Waxwings use a wider variety of fruit trees in more open and edge habitats. Bohemians are more specialized on certain trees like mountain ash and ornamental crabapples found in older, northern forests.
So while both wander nomadically in winter seeking fruits, their breeding habitats show some differences. This likely limits flock mixing opportunities.
Conclusion
In summary, Bohemian Waxwings and Cedar Waxwings do occasionally mix together into temporary multi-species flocks, especially in winter and when feeding on abundant fruit sources.
However, their breeding ranges and habits do not overlap very much which limits opportunities for flock mixing. Even in winter, Bohemians seem to favor some different food sources and wander more unpredictably than Cedars.
So while flock mixing occurs on rare occasions, most evidence indicates the two species maintain stronger social ties and flocking behavior within their own species the majority of the time. Their niches and needs show enough subtle differences that they do not regularly comingle.
References
Key Sources
Witmer, M.C., Mountjoy, D.J. and Elliot, L. (2014). Cedar Waxwing (Bombycilla cedrorum), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA. https://doi.org/10.2173/bna.309
Witmer, M.C. (2017). Bohemian Waxwing (Bombycilla garrulus), version 3.0. In The Birds of the World (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.bowax.03
Dunn, J. L., & Alderfer, J. K. (Eds.). (2011). National Geographic field guide to the birds of North America (6th ed.). National Geographic Society.
Other Sources
Audubon Guide to North American Birds. https://www.audubon.org/bird-guide
All About Birds. https://www.allaboutbirds.org/
eBird. https://ebird.org/home
Merlin Bird ID. https://merlin.allaboutbirds.org/
The Cornell Lab of Ornithology. https://www.birds.cornell.edu/home/
Sibley Guides. https://www.sibleyguides.com/