Year of the Bird Series: June– Rose-Breasted Grosbeaks

Article by Chris Harris, Environmental Physiology Technician at the University of Windsor

It is never difficult to tell when a rose-breasted grosbeak is being banded and processed in the banding lab. What begins as a mysteriously unremarkable bird bag immediately begins squeaking like a particularly angry dog toy when it is picked up. New banders learn that carelessly rummaging in that bag can result in an unexpected role-reversal when the grosbeak’s seed-eating bill grabs them first, suddenly leaving the bander as the one squeaking instead. With a bite that reminds me of my sister’s pinching phase during her preteen years, rose-breasted grosbeaks provide my favourite style of lesson in proper songbird handling techniques: painfully memorable, but ultimately harmless.

Aside from testing the toughness and commitment of new ornithologists, their abundance, tolerance of humans, and eye-catching appearance has made the rose-breasted grosbeak a frequent introductory species into the world of birds and birdwatching. The spring arrival at a backyard feeder of a black and white bird with a pinkish red throat and underwing has sent many rushing for a field guide to find out what this new bird could be that looks so striking and different from the familiar, year-round resident species they’ve watched all winter. Hopefully, once the new birdwatcher identifies that their feeder bird is a male rose-breasted grosbeak, they will continue reading about this species as it is the perfect ambassador for all birds.

First, when females arrive a few days later, the new birdwatcher will very quickly learn about sexual dimorphism given that females look completely different with their streaky brown and white plumage and yellow underwing. They may also notice a juvenile male and learn about molt and plumage maturation since juveniles retain their first flight feathers and juvenile males usually look mostly like a female but with a few male features such as pink in the throat and underwing. Rose-breasted grosbeaks are also long-distance migrants. A quick look at their range map will show that the first male arriving at the feeder was wintering in Central America or northern South America only a month prior. While breeding, both sexes sing, incubate, brood, and feed. It is rare for so many broad, core concepts of birds to be demonstrated so obviously in a single species.

Adult male and female rose-breasted grosbeak: different looks, same beak and attitude (Photo uncredited)
An example of the mixed appearance of a recently fledged male, he won’t reach perfect black, white, and pink until he is 2 years old (Photo uncredited)
A male rose-breasted grosbeak developing a taste for bander (Photo uncredited)










A second reason the rose-breasted grosbeak is a perfect introduction to birds is that they exemplify the contradictions and complexity of relationships between humans and wildlife. They are considered by some to be beneficial for eating several agricultural pest insects and yet by others as a pest since they also eat buds, flowers, and fruit themselves. Their abundance and large breeding range in deciduous and mixed forests throughout eastern and central North America has led to them to be considered a forest edge species resistant to human impacts and disturbance and of little conservation concern. However, a recent series of studies suggest their breeding success may be sensitive to forest patch size and that many of the individuals that we see breeding in edges, backyards, and gardens face numerous threats and have too low a success rate to replace themselves. What appears as a common and widespread breeder comfortable in disturbed habitats may instead be a population that relies heavily on a few core, high-quality breeding areas. This demonstrates both a big limitation of using presence and abundance alone to measure population health and an all-too-frequent mechanism of sharp population decline in other species.

The last reason why they are a perfect example songbird is that, despite being a common and well-loved feeder bird, they are not well studied and there are a great many things we don’t know about the species.  Very little is known about crucial details like survival rates, nesting success, time budgets, nestling diet, wintering, and migration. Much of what we do know is built upon anecdotal observations of a few individuals many years ago. For example, the knowledge that their diet is composed mainly of insects, seeds, and fruit, and even that they eat both crops and crop pests, comes mainly from a study of stomach contents from 1908 and a few supporting anecdotal observations in the intervening century. In the last 50 years, there are only a handful of studies on behavior, hybridization, and the impacts of forest management on breeding. Surprisingly, we often know even less about many other species of birds. So, whether you are just discovering birds or becoming reacquainted with an old favourite, take some time to look a little more closely at the rose-breasted grosbeak, they always have something to teach you.