We sorted out the warblers into three major forms based on the dominant colouration: the greens-and-grays, the yellows (with black, gray and green), and oh-those-astoundingly-coloured-ones. We were able to watch and photograph representatives of all these forms in and around our home in the Commonwealth Terrace Co-operative (CTC), the student housing area of the University of Minnesota (UMN). The CTC has excellent flowering trees planted by residents and the management (see photos below).
CTC abuts the Sarita Wetland, which is maintained by various groups at the UMN, and has many more native trees, shrubs, and of course, a wetland (photo below).
Warblers are mostly insectivorous with few species also eating nectar. As a consequence they are most active on sunny days and on foliage or flowering plants that are warmed by the sun. In spring most male warblers assert themselves vocally, and mornings in wooded areas are filled with their cheery trills, chirps, and bzzzes. The first few warm days after winter are the best for warblering (we know that is not a real word, but strongly feel that it should be!). The trees are just regaining their leaves then allowing excellent views of the birds as they jump, sally, chase and dangle acrobatically from leaves, branches and tree bark chasing caterpillars and invertebrates. Tree canopies literally quiver with hungry warblers during the peak of the migration! Waves of individual species are apparent. In 2008, the Yellow-rumped Warblers got to CTC first as soon as the last snows melted, with the rest of the species following behind nearly a week later. Females of many species have very similar colouring to males, but few are starkly boring compared to their stunning male counterparts. We saw more females of most species later in the migration season, and wonder if females take another route, or if they come through later and in smaller, less conspicuous parties.
Small parties foraged high in the canopy for insects, while several birds fed on nectar on flowers below. Plum trees planted by CTC residents and the chestnut trees planted by UMN were in flower, and Tennessee Warblers getting at the nectar was a regular sight. The Bird Guide of the Cornell University describes this species as a “nectar thief” avoiding pollinating flowers by making a hole at the base of flowers to get at the nectar avoiding pollinating the flower. At least on the Plum and chestnut trees, this was not true. Birds feeding on nectar on these flowers took nectar without making a hole at the base, and carried pollen at the base of their beaks (see photo above) indicating that they were pollinating the flowers. CTC residents likely owe many of their Plums to this bird!
We saw this species only thrice at Sarita; they seemed to favor the Elm trees that were in flower. Despite its name, very few males apparently have the orange crown, but the rest of the features – eye ring, grey neck and belly, yellow wash on breast and belly, and no prominent markings on wings or the back – distinguishes this warbler from other species despite its overall dullness. This species was more like the warblers we were used to in India.
This is a classic example of a gleaning bird! It was common at CTC and Sarita. Individuals were clearly territorial and sightings were certain on some Elm trees. The white eye ring, dull-green on the back, yellowish-green on the belly and throat on a gray-headed bird made it easy to identify.
This was a common warbler, among the first to appear along with the Yellow-rumped Warbler in mid-April. It was never in very large numbers, but individuals could always be seen well spaced out at CTC, Sarita and the Trolley Way during every visit. We observed this species catching insects mostly by gleaning, but a few times by sallying. It frequented the higher branches apparently favouring the top-most leaves rarely making forays into the lower branches. The all-yellow bird has chestnut streaks on the breast making it impossible to misidentify.
Clearly our favourite warbler in the New World! In coloration, this species fits into our classification of being a oh-those-astoundingly-coloured warbler. This was one of the species that followed the initial wave of Yellow-rumped, Yellow and Tennesse Warblers. This species was never seen in large numbers. We saw several singing males at Trolley Way and Sarita, but never saw signs of nesting. This species appeared to prefer lower and middle-storey branches, and systematically searched all leaves, buds and flowers along a branch before flying to the next branch. We saw it feed with vireos, flycatchers and other warblers.
Female of Magnolia Warbler
Cape May Warbler
Female of Cape May Warbler
Female of Yellow-rumped Warbler
The tail wagging combined with the rust-coloured cap gave away the identity of this warbler. We saw this species foraging in a variety of conditions that included pine trees, tree canopies, mowed grass, and low shrubs. This was an uncommon warbler at CTC and Sarita, and we saw several more on the University campus especially on The Hill.
Female of American Redstart
Female of Common Yellowthroat
At CTC & Sarita, and outings to other warbler locations while in the mid-west, we enjoyed the company, food, birding skills and knowledge of John & Cathy Ley, Scott Loss, Derric & Kelly Pennington, and Jon & Karen Slaght. CTC & Sarita wetlands together constitute a superb urban hotspot for birds, along with several other small patches of woodlands and wetlands in the vicinity. These are managed by a very large number of people including professors and student groups from CTC and UMN. Recent discussions to initiate a birding e-group and monitor the birds here are very encouraging, but alas – come a little too late for us as we are moving back to India soon.
Cornell Laboratory of Ornithology: All About Birds. http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/
Some useful websites for warblering: