Being in the American mid-west has several distinct attractions for bird-brains. We have previously described one such attraction – experiencing the lekking behaviour of Prairie Chickens. This blog entry describes another – warblers in breeding plumage. The mid-west experiences two annual deluges of warblers. The fall migration occurs during September and October when warblers have completed their breeding in the northern climes, and are headed to their wintering areas in the warm south. At this time, bird-watchers are challenged by the similar plumages of several species. This blog is about the second deluge – the spring migration in April and May. We focus on warblers we were able to photograph in their breeding finery in the spring of 2008. Being birders from Asia, where the word “warbler” means “dull green or brown bird”, we have been completely captivated by the New World warblers. This is our modest attempt at celebrating these incredible birds.
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). 
A small walk toward the UMN on Cleveland avenue brings us to the “Trolley Way” or the Lauderdale Nature Area, a beautiful small patch of wilderness amid an otherwise buildings-dominated area (photo below).
Together, these three spots have a large variety of habitats and food sources within a relatively small area, and attract an incredible number of bird species. The best part of this set-up for us was the ease with which we added new species to our list; we only needed to step outside our apartment!
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.
Golden-winged Warbler
We saw only two individuals of this species at the Trolley Way. This is a species of Federal Concern that requires habitats of medium openness. It forages mostly on the upper canopy making photography difficult as is evidenced by the not-so-good photos we were able to get. We first heard the low but distinctive bzzz calls (thanks to the sharp ears of our friend Derric) before we saw it.
Tennessee Warbler
On May 15-17, this was the commonest warbler at CTC and Sarita. Calls of this bird could be heard from nearly every tree and bush. It is not very bright, but the green back, dark wings, the gray head with a prominent white eye-brow (or supercilium in bird lingo), and a dull gray band over the breast standing out on an otherwise white neck and belly make it very easy to identify. Females have much duller wings.
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!
Orange-crowned Warbler
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.
Nashville Warbler
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.
Northern Parula
We saw this bird in small numbers in the Trolley Way. Views were invariably of individuals very high up feeding in the middle-level branches of tall oaks, and we were unable to get good pictures of this bird. We did not see this species at CTC or at Sarita during our stay.
Yellow Warbler
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.
Chestnut-sided Warbler
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.
Magnolia Warbler
Female of Magnolia Warbler
Another member of the yellows, the Magnolia Warbler was, to our delight, a common warbler at CTC and Sarita. We also always saw it at the Trolley Way and in different locations on the University campus. Again, though never in large numbers, few were always present throughout the spring and early summer. These also seemed to use the middle-storey branches once the leaves were out, though foraged just about anywhere on the tree when the leaves were just buds.
Cape May Warbler
Female of Cape May Warbler
Despite being markedly yellow, the gorgeous combination of brick-red and yellow on the cheeks and ash-black on the head on the male combined with the distinctly streaked bright-yellow neck and belly had us classifying this species as one of the oh-those-astoundingly-coloured-ones. It is unique among warblers in having a tubular tongue that is used to collect nectar during winter. We saw this species only once at CTC (photographs) and a couple of other times on flowering bushes on Como Avenue, always with Tennessee Warblers.
Yellow-rumped Warbler
Female of Yellow-rumped Warbler
The warbler migration of 2008 was heralded by large flocks of the Yellow-rumped Warblers. The strategically placed yellow markings on this otherwise dull-grey and black bird convert it into an attractive warbler. The female is very similar to the male, but is markedly duller.
Black-throated Green Warbler
The name describes this species nearly in entirety missing out only on the bright white belly and sides streaked with thick black markings. This species arrived in the second wave along with the Tennessess and Nashvilles, and shared much of the same habitats and habits of the latter. This species was an ace gleaner jumping, diving and flying to catch ants and other invertebrates below leaves and on buds. We seldom saw this species in the lower branches or on the outermost leaves. Singing males were not uncommon at CTC and Sarita in late May and early June, but we could find no evidence of nesting.
Blackburnian Warbler
Being the only warbler in North America with an orange throat, a male in full breeding plumage is impossible to mistake. We saw only two males in CTC, and managed to photograph one.
Palm 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.
Black-and-white Warbler
The first individual of this species we saw was during the second wave, but then it became one of the most regularly sighted species of warblers at CTC and Sarita. This species feeds almost entirely on invertebrates on the bark of trees using a nuthatch-like behaviour of creeping along tree-trunks and branches. The male and female are very similar.
American Redstart
Female of American Redstart
Rather different from the Redstarts we were used to in Asia, this incredibly active warbler was one of the first species to arrive with the Yellow-rumped Warbler. However, it was never seen in large numbers. Males arrived first and appeared to be setting up territories in which they displayed using song and displays (see photograph). Females arrived nearly a fortnight later at CTC and Sarita. These warblers were the hardest to photograph since they are reluctant to waste anytime sitting still. Most of the time, the fan-like tail was the only thing that was visible in the canopy. Individuals were very curious and approached us when we began watching them, then quickly lost interest and disappeared into the canopy looking for food. Males are marked with orange on the shoulders and on their tail that is replaced by yellow in the females. We suspect a pair to be nesting in Sarita but never did see any confirmed sign.
Common Yellowthroat
Female of Common Yellowthroat
It is hard to be certain when this species arrived. We saw few individuals during every outing at CTC, Sarita and the Trolley Way. Males were much easier to see compared to the duller females that lack the black-and-ash mask of the male. We saw two males displaying and singing in Sarita but never managed to find a nest if there was one. This species rarely, if ever, climbed onto trees and most of the foraging appeared to be done in the undergrowth and on litter. It was also the most shy of the warblers we watched.
Wilson’s Warbler
Next to the Orange-crowned Warbler, this was the rarest warbler at CTC and Sarita. It appeared to have arrived in the second wave of migration. Individuals favoured the upper canopy and rarely came out to the outermost leaves to feed making photography and observations difficult. We never saw it on trees and shrubs that flowered in profusion. The species is all yellow except for the black cap and grey wing-tips and tail. It ranked among the top acrobatic warblers we observed in the mid-west.
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.
Bibliography:
Cornell Laboratory of Ornithology: All About Birds.
http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Some useful websites for warblering:
http://www.trmichels.com/NatureToursMNBirdsList.htmhttp://www.schmoker.org/BirdPics/Warblers.html
