Warblers

All posts tagged Warblers

By: Ian Stewart, Ornithologist

Delaware birders are out in full force at this very moment and one of their main targets is migrating warblers. Warblers are small, colorful songbirds which flit actively from tree to tree picking off insects with what the field guides usually describe as thin pointed beaks (also known as ‘bills’). But are warbler beaks really all small and pointed? We have handled several warblers during the Delaware Nature Society’s bird banding project and a closer view reveals a surprising amount of variation in the size, shape and color of their beaks.

The Northern Parula is one of the smallest warblers and has a very thin and pointed beak which it uses like fine tweezers to glean tiny arthropods from leaf surfaces.

Northern Parula

Northern Parula

The Prairie Warbler also has quite a sharp beak but it is shorter and more rounded than the Parula’s. Its beak is jet black unlike many of the other warblers which have brownish two-toned beaks with the upper mandible being darker than the lower.

Prairie Warbler

Prairie Warbler

The Mourning Warbler has a fairly substantial bill for a warbler. Mourning Warblers tend to feed on or near the ground and perhaps eat larger insects or grubs.

Mourning Warbler.

Mourning Warbler.

Waterthrushes are relatively dull, streaky warblers that live along streams where they pick arthropods from the surface of the mud and rocks. There are two species, the Louisiana and the Northern, which look very similar but can be partly distinguished by their beak length. The Louisiana was once known as the ‘large-billed waterthrush’ and you can see from these photos that their beak is indeed longer and a little heavier than the Northern.

Louisiana Waterthrush

Louisiana Waterthrush

Northern Waterthrush

Northern Waterthrush

The American Redstart has an unusual beak for a warbler. When seen from above (or more commonly, from below!) its beak is broadly triangular and looks more like that of a flycatcher than a warbler (see the photo below). It’s probably no coincidence that Redstarts often feed by leaping off branches and grabbing insects in mid-air. The conspicuous bristles around the base of their beak may help them trap these insects.

American Redstart (left) and Northern Waterthrush Beaks

Comparison of beak thickness in American Redstart (right) and Northern Waterthrush (left)

Another warbler with an unusual beak is the Yellow-breasted Chat. The Chat is a large, stocky bird that some people do not even consider a warbler, and it has a correspondingly huge, stout beak with a rounded upper mandible. Chats have such a big beak that they can chomp on insects such as grasshoppers that that are too big for the other warblers and can also eat berries.

Male Yellow-breasted Chat

Male Yellow-breasted Chat

Insects and other arthropods are the staple food of all warblers and yet the variation in the size and shape of their beaks suggests that each species eats different prey. This partly explains why some species are usually seen actively hunting in the upper canopy of either deciduous or pine trees while others creep slowly around on the ground, perhaps waiting for an arthropod to emerge. Warblers are passing through Delaware as we speak so next time you see one, take a good look at its beak and see if you can guess what it feeds on!

By Joe Sebastiani, Seasonal Program Team Leader

In the autumn, the best bird feeder in my yard is not plastic and filled with seeds…it is an American elm tree.  This tree, which was planted in the backyard 10 years ago literally swarms with aphids each and every fall.  They buzz around the tree, line every crack, and coat every branch.  Walking past the tree, you must go through a fog of these tiny, winged insects. 

This is the American Elm in my backyard that attracts zillions of aphids in the fall. In turn, lots of migratory songbirds feast in the tree.

These little insects attract small songbirds which gorge themselves at this tree from about mid-September through October.  Earlier this year, a Cape May Warbler spent two days feeding at the tree.  This week, a Brown Creeper inched its way up the trunk, plucking aphids at every hitch.  Today, however, was the big show of the season so far.  At about the same time, the following species were in the tree feeding: Ruby Crowned Kinglet, Golden-crowned Kinglet (several of each), Blackpoll Warbler, Tennessee Warbler, Yellow-rumped Warbler, Palm Warbler, Northern Parula, Magnolia Warbler, Nashville Warbler, and a Downy Woodpecker.

This Northern Parula hung around the tree for a while, getting its fill of aphids.

This Blackpoll Warbler fed on the tree all morning. It was very tame and allowed a close approach. Here it is picking an aphid off a branch.

This Palm Warbler stopped in briefly to feed at the American Elm.

I watched the birds feed for a few hours this morning.  Mostly, they allowed me to get quite close, since they were very preoccupied with feasting on the thousands of insects that coat the tree.  Later in the morning, I saw a chickadee getting in the act as well.  Since I’ve never seen a chickadee eat the insects before, I looked a little harder.  It turned out to be a Black-capped Chickadee, which is rare where I live in southern Chester County, PA.  My resident Carolina Chickadees would rather stick to the plastic kind of feeder filled with seed. 

I was very surprised to see a Black-capped Chickadee feeding in the tree on insects. This bird is a rare migrant where I live near Kennett Square, PA. The resident Carolina Chickadees pay no attention to the aphids, preferring to feed at the regular bird feeder.

This is exactly why we should plant native plants in the backyard.  Native plants attract insects which attract birds and other predatory insects and so on.  Today I can see how even just one tree can support dozens and dozens of birds, possibly hundreds over the course of the fall migration when they stop to refuel here. 

Ladybug Beetle larva are also attracted to the elm tree to eat the aphids. Check out the winged aphids all around the larva.

American elms have mostly succumbed to the introduced Dutch Elm Disease and there are few in the ecosystem around us.  My elm is genotype that has been developed that is resistant to this disease.  Just imagine the impact American elms had in the ecosystem when they were commonly found in our area.

This Ruby-crowned Kinglet hovers to pick aphids off a leaf.

You can see some of the aphids buzzing around the head of this Tennessee Warbler, which was another fantastic bird to see in the tree.

For more information on native plants in the backyard landscape, check out Bringing Nature Homeby Douglas W. Tallamy.

By John Harrod, Manager, DuPont Environmental Education Center

Earlier this week, while walking along the Wilmington Riverfront on a relatively warm day in February, I spotted a bird that most people might not expect to see in the city. I wasn’t surprised to see it, though, since the plantings along the Riverfront include northern bayberry (Morella pensylvanica), one of this bird’s favorite winter foods.

 What was it?…a Yellow-rumped Warbler, or as it is known to some birders, the “Butterbutt.”

Yellow-rumped Warbler. By Alan D. Wilson, www.naturespicsonline.com

Yellow-rumped Warbler. Photo by Alan D. Wilson, www.naturespicsonline.com

Identified by the distinctive yellow patch on their rump, these warblers are fond of the waxy, white fruit of the bayberry and its southern counterpart, the wax myrtle (Morella cerifera). Every year these birds winter in Delaware and can easily be found along the coast where Morella is prolific. They also winter in the Midwest and southeastern U.S., although there they rely on alternate food sources such as berries of the eastern red cedar and poison ivy.

Bayberry fruit. Photo by John Harrod

Bayberry fruit. Photo by John Harrod

I don’t expect you to run out and plant poison ivy, but bayberry is definitely garden-worthy. In the landscape, bayberry averages 9 feet tall and grows in full sun to part shade, thrives in poor, sterile, sandy soil, and even performs well in heavy clay soil. (An interesting side note: The plant also provides the scent for “baybreeze” candles.) If you like the idea of adding bayberry to your yard, plan to pick up a few of the plants at the Delaware Nature Society’s Native Plant Sale the first weekend in May.  Plant it and they will come!

Yellow-rumped Warbler in a bayberry on the Wilmington Riverfront. Photo by John Harrod.

Yellow-rumped Warbler in a bayberry on the Wilmington Riverfront. Photo by John Harrod.

 If you would like to learn more about attracting wildlife to your property or certifying it as an official Backyard Wildlife Habitat, visit the Delaware Nature Society’s Backyard Wildlife Habitat webpage: http://www.delawarenaturesociety.org/bwh.html.