Migration and Orientation; Homing Pigeons and Pigeons Gone Bad

By in Behavior, Migration

The fall migration is on the decline now with most of our flycatchers, swallows and warblers gone for the next seven months. All of these birds depend on insects for their sustenance, a resource in short supply now.

Sparrows and other seed-eaters have a more leisurely migration. They can find seeds, at least until the first snows arrive. Even so, by the end of the month most of our sparrows will be gone to more moderate southern areas.

As I discussed in the last column, we know that the majority of migratory bird species have an innate knowledge of where they should go to spend the winter. It boggles the mind to realize that many first-year birds find their way unaided by adults to their wintering habitat they have never seen. Travel instructions are encoded in their genes.

More

Fork-tailed Flycatcher

By in Behavior, Migration

Fall migration always has some surprises in store. One of the most delightful vagrants this fall was a Fork-tailed Flycatcher. This species normally occurs from Mexico all the way south to Argentina. A few vagrants occur along the eastern seaboard every year, usually between September and November.

The Maine bird was found at Gilsland Farm in Falmouth on September 16 by a local birder, Angus King. The electronic word got out and dozens of birders got to see the impressive bird. Alas, it was last seen on September 19.

Fork-tailed Flycatchers are white underneath with a gray back and a bold, black cap. The hallmark of the species is the fantastic tail. The outer tail feathers are ridiculously elongated. In flight, the tail feathers spread to make the distinctive fork. The tail of a Fork-tailed Flycatcher is like the tail of a Barn Swallow on steroids!  Relative to body size, the tail of a Fork-tailed Flycatcher is the longest of any bird, two to three times the body length. Females and young birds have less ostentatious forked tails.

More

The Impact of Hurricanes on Birds

By in Weather

The southeastern United States and the West Indies have suffered the fury of the Hurricanes Harvey and Irma in the past few weeks. We soon know the impact on humans and buildings after the storms pass. But what is the effect on birds? How do birds weather the ferocity of a hurricane?

Our understanding of the behavior of birds during a hurricane is necessarily incomplete. No ornithologist is going to risk life and limb to try to make observations in the torrential wind and strong winds of a Type V hurricane!

Let’s first consider land birds. A land bird caught up in the winds of a hurricane is very likely to perish. Such a bird certainly cannot buck the wind to find safety. As a storm builds, land birds seek out shelter. Perhaps a tree cavity, a small hole below a tree root. A dense thicket, a stout tree. These microhabitats provide effect refuges from the wind and rain.

More

Shorebird Foraging Behavior

By in Behavior, Foraging

Shorebird migration is in full swing. Many of these migrants have nested on the arctic tundra and are heading for Central or South America to overwinter. These trips demand lots of fuel so our shorebirds must feed voraciously.

Most shorebirds are fairly confiding birds so it’s easy to get close enough to watch their feeding behaviors. Our shorebirds show a diversity of foraging techniques.

Let’s start with the plovers. Semipalmated Plovers, Black-bellied Plovers and American Golden-Plovers, all common fall migrants in Maine. Plovers rely on their eyes to find food on intertidal mudflats. The plovers practice a type of feeding that animal behaviorists called run-and-peck. A plover will stand in one spot on the intertidal surface and keep an eye out for movement at the surface of the sediment. The plover will run over and grab the unsuspecting arthropod or marine worm.

More

Taxonomy Above the Species Level

By in Taxonomy

Humans have a penchant for organizing. We like order. This need for organization certainly drove Karl Linnaeus, a Swedish naturalist, to published the first catalog of life, the Systema Naturae, in 1735. He devised the framework we still use in our taxonomy.

In the last post, we explored the challenges of recognizing species. New knowledge forces us to re-examine our understanding of the limits of variation of species. We regularly gain or lose species on our life lists as former species are divided into two or more new species or others combined into a single species.

Taxonomists do have methods for defining a species. The problem is that there is more than one method and the different approaches do not always get to the same conclusion!

More

What Is a Species?

By in Speciation, Taxonomy

This post is a follow-up to the previous one in which I discussed some of the recent decisions by the North American Checklist Committee. This committee of ornithologists makes decisions on whether some species should be split and others should be combined into a single species.

Many were surprised that the Committee did not vote to split the Yellow-rumped Warbler into three species. The votes on this issue was not unanimous. Today, we will discuss three different definitions of species, each of which has its champions.

The first efforts to classify life on earth hinged on a morphological definition of species. Individuals that look alike are combined into a single species. This definition works pretty well for most birds. However, pitfalls lurk.

More

AOS Checklist Report

By in Speciation, Taxonomy

In early July, many birders eagerly await the annual report of the American Ornithological Society’s Committee on Classification and Nomenclature of North and Middle American Birds. This committee of professional ornithologists is responsible for making decisions on the splitting or lumping of species, changes in common and scientific names of birds and changes in the order in which birds appear in official checklists.

Like any scientists, ornithologists revisit bird identification and classification as more information becomes available. Requests for consideration of thorny taxonomic problems are accepted by the Committee and sometimes the Committee decides to reconsider decisions on their own.

More

June Vagrants in Maine

By in Behavior, Migration

Roger Tory Peterson once quipped that birds have wings and they use them. One of the thrills of birding is seeing birds that are either passing through or lost. A vagrant bird can really spice up a daily bird list.

We are accustomed to seeking out rarities during the concentrated spring migration or the more leisurely fall migration (August into November).  In June, most birds should be on their breeding grounds.

Contrary to this logic, June brought some remarkable rare birds to Maine this year. On June 7, a Burrowing Owl was photographed near the Katahdin Inn in York. At this time of year, Burrowing Owls should  be in the western half of temperate North America, nesting in abandoned prairie dog burrows on the plains. There is also a disjunct population in Florida. Unfortunately, the owl was a one-day wonder. If accepted by the Maine Bird Records Committee (hereafter, MBRC), this bird will be only the second ever found in Maine. The first Burrowing Owl lingered for over a month in late summer in Washington County in 2006.

On June 9, an apparent drake King Eider was sighted off Potts Point in South Harpswell. The written description and fuzzy photographs (taken from a long distance) support the identication. These birds breed in the high Arctic; an adult male in Maine in June is peculiar, indeed.

On June 12, a Magnificent Frigatebird was photographed while perched on Stratton Island and was seen later that day from Prouts Neck as well as Pine Point. The bird could not be relocated the following day.  The MRBC lists eight records of this tropical species in Maine, none of which have been reviewed to date.

A Magnificent Frigatebird was seen off Salisbury Beach on the North Shore of Massachusetts on June 14. Perhaps it was the same bird that was found in Maine.

In an amazing contrast, a Snowy Owl was photographed on June 13 in a driveway in Freeport, near Hedgehog Mountain Park. Snowy Owls should be nesting on the arctic tundra at this time of year. Normally, more than 2,000 miles separate frigatebirds and Snowy Owls in June.

Why not add some western vagrants to add to the mix? On June 13, a Snowy Plover was found with Piping Plovers at Reid State Park.  If accepted by the MBRC, the Snowy Plover will a new addition to the official Maine bird list. On the same day, a Townsend’s Solitaire was photographed in Whitneyville. Townsend’s Solitaires do wander regularly to eastern North America but a June record is quite unusual.

And the hits keep on coming. On June 20, a Brown Pelican was photographed off the Prouts Neck Yacht Club. The bird was seen regularly through June 23 by many birders. The bird split its time among Prouts Neck, Stratton Island, Bluffs Island and Pine Point.

The plumage and the presence of a pale stripe on the lower part of the throat pouch indicate this bird was in its second year of life.

The MBRC lists one accepted record for Brown Pelican in the state, a bird seen on June 16 in Harpswell. Four older records from 1826, 1914 (2 records) and and 1922 have yet to be reviewed by the MBRC.

Despite diligent searching on June 24, the pelican could not be located in Maine. However, a Brown Pelican was seen in Rye, New Hampshire on that day. This bird was also a second-year bird and may well have been the same bird seen in Maine. Two additional Brown Pelicans were reported from Salisbury Beach in Massachusetts.

New Hampshire birders enjoyed the first record of another tropical vagrant, a Brown Booby. This cooperative bird was found at Cobbett’s Pond in Windham. Here’s a remarkable YouTube video of this delightful bird http://bit.ly/2sk2dJE They are normally found no further north than the Caribbean.

[First published on July 2, 2017]

 

 

Ruby-throated Hummingbirds

By in Species Accounts

The hummingbirds are back! Who among us has not joyfully exclaimed when the first Ruby-throated Hummingbird of the year appears at our flowers or feeder? It’s hard to think of a Maine migratory breeding bird whose spring arrival is more eagerly anticipated.

The hummingbird family is restricted to the New World with most of the 328 species occurring in Central America and South America. Unsurprisingly, south Texas and southeastern Arizona have the highest hummingbird diversity in the U.S. with almost 20 species in each area. For us New Englanders, we have to be content with a single species.

But, our Ruby-throated Hummingbirds have a broad nesting distribution, occurring in the United States east of 100 degrees latitude everywhere except the southern tip of the Florida peninsula. In Canada, ruby-throats occur from the Maritime Provinces westward into Saskatchewan. No other species of hummingbird in North America has a broader geographic range.

The delights of watching Ruby-throated Hummingbirds are many. The red throat feathers (called a gorget) of a male Ruby-throated Hummingbird may seem to sparkle in the right light.  Their throat feathers refract light, giving the bird an iridescence that makes the feathers seem to shimmer as the bird moves its head.

Who isn’t amazed by a hummingbird’s ability to fly backwards? Unlike other birds that extend their wings down and forward during a powerful downstroke and then fold the wings to raise them back for the next downstroke, hummingbirds generate lift and thrust on both the downstroke and upstroke. Their wings in motion describe a figure-8 when viewed from the side. At the end of the downstroke, the wing is moved backwards and power is created by the upstroke moving forward to the head.

Don’t expect to see these amazing wing movements with your naked eye. Hummingbird wings are a blur in motion; the wings beat up to 70 times a second. Slow-motion video is needed to see the figure-8 wing movements.

Ruby-throated Hummingbirds have a mating system called promiscuity. Each male tries to mate with as many females as possible. No long-lasting pair bonds are forged.

A male will court a female through complicated flight displays. When a female flies into his territory, he begins with a dive display, flying U-shaped loops starting from as high as 30 feet above the female. If the female perches, he switches to very fast, side-to-side flights, with his gorget extended, within two feet of the female. If the male is acceptable as a mate, the female will cock her tail feathers to one side and lower her wings, inviting the male to mate with her. Mating lasts only about 2-3 seconds and that is the end of the male’s contribution to the offspring.  Keep an eye out for these behaviors. I find them fascinating.

As a single mom, the female builds the nest by herself. The base is made of the down from dandelions and thistles and is attached to the upper side of a branch, much like a saddle over the back of a horse. The sides of the nest are made of plant down, bud scales and spider webs. The plant material is woven into the nest with the spider silk.

The eggs are usually two in number and, as you might imagine, are tiny. An average egg is half an inch long.  That’s barely larger than an English pea.

Incubation takes 12-14 days and the young hatch as naked, blind chicks. Feeding usually begins soon after hatching and the young fledge about 20 days after hatching.

We think of Ruby-throated Hummingbirds as depending on nectar for their nutrition. However, these birds also take spiders and insects (mosquitoes, gnats, fruit flies and small bees).  Sometimes hummingbirds steal insects caught in spider webs and may take insects attracted to oozing sap from Yellow-bellied Sapsucker wells.

[First published on June 18, 2017]

Migration Physiology II

By in Migration, Physiology

Spring bird migration has run its course. Birds are busy attracting mates, establishing territories and building nests. Before I put migration to rest, I want to add a bit on the remarkable physiological demands of bird migration and the adaptations birds have to meet those demands.

In the last column, we explored the engineering problem migrating birds have of how much fuel (fat) it bird should carry. Carrying extra fat for insurance means a bird’s mileage will be reduced because of the excess weight. Cutting the fat stores too close might mean running out of fuel and perishing.

Thanks to the work of Dr. Scott McWilliams and his students at the University of Rhode Island, we know many migrating birds have a trick up their wing to improve their flight performance.

In preparation for migration, a bird enlarges and lengthens its gut to allow it to feed more rapidly and put on weight. It’s an adaptation for gluttony. The cells of the intestines become larger and new cells are formed.

However, the physiological demands of the gut are high. So during migration, once fat stores have been loaded, a bird essentially shuts down its gut and the gut decreases in size and weight. The diversion of energy from the gut can be used to fuel the flapping of the wings for a migrating bird.

Once a bird has stopped after completing a leg of its journey, it is unable to feed efficiently because its gut has shut down. It must rebuild the gut to allow food to be digested properly.

McWilliams showed that proteins are essential to get the digestive tract functioning well. Birds that only have access to fruit at a stopover will refuel more slowly, often entailing a delay in their migration.

Let’s revisit the Semipalmated Sandpipers discussed in the last column. To fuel their four-day migration over the Atlantic Ocean from the Bay of Fundy to Suriname, the birds pig out on small crustaceans called Corophium in the upper Bay of Fundy mudflats. Dr. Jean-Michel Weber of the University of Ottawa noted that the Corophium are high in omega-3 fatty acids. He found that the efficiency of the sandpipers’ muscles increased over the two weeks or so that birds spent fattening on the mudflats.  Weber suspected that the omega-3 fatty acids might be the reason for that increase in efficiency. However, he could not rule out other reasons (hormonal changes, exercise) to explain the muscle improvement.

He resorted to some lab experiments with Bobwhite quail. These birds rarely fly and do not migrate, eliminating exercise and migration-related hormonal changes as possible factors. By supplementing the diet of the Bobwhite with omega-3 fatty acids, he found a direct increase in muscle efficiency between 58% and 90%.  These changes are similar to ones noted in Semipalmated Sandpipers shortly before they embarked on their 2,400-mile jaunt to South America. Remarkable!

Switching gears, we know that migrating birds often overshoot their intended breeding destinations. Summer Tanagers, Hooded Warblers and Kentucky Warblers occasionally appear in Maine in the spring but presumably withdraw to their more southerly breeding grounds.  These birds likely made a navigation error.

A different explanation may explain the appearance of some out-of-range birds. Recently in southeastern Florida, a number of Caribbean birds appeared to the delights of Florida birders. These birds included Bahama Mockingbirds, a LaSagra’s Flycatcher, a Fork-tailed Flycatcher, a Thick-billed Vireo, two Cuban Vireos and many Bananaquits and Western Spindalis (a type of tanager).

Why this influx of rarities? Some ornithologists believe that these appearances were driven by the devastation wrought by Hurricane Matthew last fall that hit eastern Cuba and the Bahamas with its full fury. Lots of bird habitat was destroyed. The hypothesis is that some Caribbean birds returned to their normal breeding grounds, found it to be destroyed, and kept on trucking to Florida.

[First published on June 11, 2017]

«‹ 16 17 18 19›»