Clutch Size Variation

By in Reproduction

Most of the birds in Maine are in the process of nesting now. Among the different bird species, there is great variation in many facets of reproduction. For instance, whether one or both parents brood, the type and location of the nest, the size of the eggs.

One striking feature that varies widely among different species is clutch size, the number of eggs laid in a single nesting attempt. Some birds (albatrosses, petrels, some penguins and some terns) have a clutch size of only one. Hummingbirds and doves always have clutch sizes of two. At the other extreme, some ducks and geese, pheasants and rails may have clutch sizes as high as 20 eggs. Our songbirds have clutch sizes varying between two and 12, depending on species.

Why is there such striking variation in clutch size among different species? This question has been the basis of a great deal of research. In this column, I will briefly introduce some of the findings of this body of research.

To begin, we must realize that reproduction is a taxing experience for birds. Birds that undertake a particularly heavy reproductive effort in one year may reduce their chances of surviving to reproduce the next year. Birds have to make a trade-off between producing very large clutches in a short life and moderate-sized clutches over a longer life.

David Lack, a British ornithologist, was one of the first scientists to rigorously study clutch size variation in birds. He came to the conclusion that a female bird should lay the number of eggs that will produce the most fledged, independent offspring.

Let’s consider Lack’s conclusion for three females which lay three, five and seven eggs, respectively. The female and her mate with only three eggs will probably succeed in fledging three young. The pair with five eggs will have to work harder but still might lose only one chick, fledging four young. The pair with seven eggs have bitten off more than they can chew. The demands of the seven hungry chicks are too much for the parents and perhaps four of the seven chicks will die from starvation. So, what is the best clutch size to have for this species? A clutch size of five – a trade-off between ambition and caution. The pair with only three eggs is not ambitious enough; the pair with seven eggs is too ambitious.

Ornithologists have tested Lack’s prediction by altering the clutch sizes of birds. One species that has been studied intensively is the Tree Swallow. These birds frequently nest in nestboxes at high densities, making it easy for an ornithologist to monitor large numbers of nests. Tree Swallows usually lay five eggs. Experiments are done by removing one or two eggs from some nests and placing them in other nests. After the egg-switching, some nests have three, four, five, six and seven eggs. The results largely confirm Lack’s prediction. A clutch size of five is the most productive clutch.

In other species, that have been examined, birds lay one less than the most productive clutch. Scientists believe that these birds are cutting back on their reproductive effort in a single year to increase their chances of having a long life.

Clutch size within a species often shows striking variation with latitude. The typical pattern is that tropical members of a species have lower clutch sizes than members of the same species that live in the temperate zone. For instance, female Northern Flickers that live in the tropics only lay clutches of three or four eggs while flickers in the northern U. S. A. and Canada may have ten or more eggs.

One possible explanation for this variation is the number of predators. The tropics have many more predators that are threats to eggs and nestlings, including snakes, other birds and various mammals. The chances of a nest being found and destroyed by a predator in the tropics is very high. In the temperate zone, the number of predators is much reduced. Many temperate nests are never discovered by predators.

Ornithologists therefore argue that tropical birds should not invest heavily in a single clutch because it is likely to be lost. It’s not prudent to make a large investment in a risky environment. It is much better to have a low clutch size, allowing the parents to live a longer life. With luck, one of the many clutches a female will lay over her lifetime will escape the predators. On the other hand, a temperate bird does not have the same high risk from predators so can lay a bigger clutch. It’s OK to make a large investment if there is little chance of losing it all.

[First published June 27, 2009]

Human Face Recognition by Northern Mockingbirds; “Wealthy” Song Sparrows

By in Recent Ornithological Literature, Reproduction

In the past month, two recently published research articles captured my attention. I’ll review these two studies in today’s column.

Northern Mockingbirds

The first paper documents the ability of Northern Mockingbirds to recognize particular human faces. This work is significant because it is the first research to show a wild animal can recognize individuals of a different species.

The work was done by Douglas Levey and his students at the University of Florida. The Gainesville campus has a large population of nesting mockingbirds. With 51,000 students walking around the campus, a nesting pair of mockingbirds will have around 15,000 humans walking within five meters of a nest during a nesting cycle (about 23 days). Most of these passers-by are ignored by the mockingbirds. Occasionally, a mockingbird will give loud alarm calls, dive bomb or even graze the head of a human. Levey’s team tested the hypothesis that mockingbirds can distinguish threatening humans from people that simply walk past, usually unaware there is even a nest present.

Levey enlisted the assistance of a number of students. The team located mockingbird nests, usually just a few feet above the ground in shrubbery, and set up an experimental protocol. For four days in a row, a student would walk to the nest and stand at the nest for 30 seconds. During the last 15 seconds, the student would put her/his hand on the rim of the nest. The students never touched the eggs or nestlings.

After only two days, the mockingbirds increased their aggressive response to the student even though the student approached the nest from a different direction and wore different clothing. The female mockingbird would leave the nest more quickly, alarm calling would increase and dive-bombing of the student would become more frequent. The intensity of the mockingbirds’ responses increased on the third and fourth days.

Now, the really interesting part. On the fifth day, a different student would approach the nest and stand close for 30 seconds, again with a hand on the nest for 15 seconds. The mockingbirds did not respond aggressively. The birds did not recognize this new intruder as a threat.

The ability of the mockingbirds to perceive their environment in such detail surely helps explain why mockingbirds coexist so well with humans in urban environments.

Song Sparrow

Wealth has its advantages. Well-to-do parents may send their children to the finest private schools. Presumably, such kids will have advantages in life compared to the rest of us from families with more modest incomes. However, recent work by Liana Zanette of the University of Western Ontario on Song Sparrows challenges this idea.

In particular, Zanette was interested in how food influences nestling growth and development. She began her study by raising Song Sparrow nestlings in the laboratory. Some were given only adequate food and others were given much higher quality food. The nestlings on the better diets grew larger than the nestlings on the poor diets. Importantly, the birds on the better diet developed larger brains and a larger repertoire of songs. We know that female Song Sparrows choose mates with larger song repertoires. So, based on this laboratory work, Zanette expected better-fed nestlings in the field to thrive.

In British Columbia, Zanette mapped the territories of a number of Song Sparrows. She put out bird feeders in the middle of half of the territories. Thus, half of the Song Sparrow pairs in the study had access to extra food. The remaining territories had no feeders and served as an experimental control.

As expected, the parents on the territories with bird feeders had more energy they could devote to their reproductive effort. Zanette expected that those females would lay larger eggs than the females on the control territories. Larger eggs lead to larger nestlings with larger brains and, for males, larger song repertoires.

In fact, just the opposite result happened. Eggs and nestlings from food-supplemented pairs were smaller those from control pairs. Rather than produce higher quality young, the Song Sparrows with supplemental food produced more eggs. The eggs were smaller on average than those produced by females on control territories. The male nestlings grew up to develop smaller song repertoires than males from control territories. The females chose quantity over quality.

The parents on a food-supplemented territory had to spread the food they collected for their nestlings among more individuals. So much for the idea that wealthy parents produce offspring with significant advantages!

Zanette found that food-supplemented parents gave more food to the oldest male nestlings. That preferred treatment allowed the sons to become as large as nestlings from control areas. However, their brain growth never caught up.

[Originally published on June 13, 2009]

Review of Life List by Olivia Gentile

By in Book Reviews

It all began with a Blackburnian Warbler in the spring of 1965. Phoebe Snetsinger was living in Minnesota with her husband and four children. She was 34 years old. A neighbor invited Phoebe to go birding with her. Phoebe’s glimpse of the brilliant orange throat of the Blackburnian Warbler marked the beginning of a burning interest, even an obsession, with birds.

To cut to the chase, Phoebe became the first person to see 8,000 species of birds. With roughly 10,000 species of birds in the world, that achievement is truly remarkable.

The story of the successful quest to see 8,000 species is chronicled in Olivia Gentile’s excellent biography, Life List. Gentile weaves two threads throughout the biography: a description of many of the adventure-filled trips Phoebe took over the years to add to her life list and an examination of Phoebe’s personality, motivations and family relationships. Phoebe largely lived her life on her own terms.

In 1967, the Snetsingers moved to the St. Louis area. Phoebe joined a nature club in Webster Groves. She was a regular on the club’s Thursday’s birding trips. Her skills grew. Her competitive spirit pushed her to surpass the record of 275 species seen in one year in the St. Louis area.

In 1969, the American Birding Association was born. The goals of this organization were to promote the competitive aspects of birding, to promote birding as a sport. Each year, the ABA publishes life list totals for various regions (state lists, North American lists, world lists). A member of the Webster Groves club, Bertha Massie, inspired Phoebe. Bertha had seen over 3000 species of birds in the world and she had the highest world life list of any woman at the time.

Phoebe’s father died in 1971. He had established a hugely successful advertising firm. Phoebe inherited a portion of her father’s wealth that gave her the means for all the international travel to come.

She took a birding trip to the Galapagos Islands in 1976 with her son and another to Kenya in 1977. On the latter trip, she saw 600 species of birds, nearly doubling her life list. She was hooked!

In 1981, Phoebe found a lump in her armpit that turned out to be a malignant tumor. Although tests showed the cancer had not spread, doctors gave Phoebe a devastating prognosis: three more months of good health and death within a year.

Phoebe decided to go on an Alaskan birding trip that she had signed up for before her cancer diagnosis. The trip went well and set the tone for much of the rest of her life. In her words, she was birding on borrowed time.

A year later, Phoebe was feeling fine and the cancer had not spread to other parts of her body. The cancer would appear two more times in her lymph nodes over the rest of her life but never metastasized.

Phoebe began traveling widely on birding expeditions. The attainment of one threshold, like 5000 species on her world life list, led her to want more. She ultimately decided to shoot for the goal of 8000 species. Gentile chronicles Phoebe’s successful quest in an engaging style.

Phoebe was a meticulous note keeper. She maintained an extensive collection of notecards on every bird she saw. During the last 15 years of her life, she was usually birding in far-flung places for at least half of the year and writing up her notes the rest of the time.

Phoebe was a headstrong woman. She broke some bones in her right wrist on one trip but soldiered on lest she miss a life bird or two. Her wrist never fully recovered. She noted the recurrence of her cancer before one trip but decided to wait for treatment until after the expedition! She suffered a brutal assault in Papua New Guinea.

Phoebe’s accomplishments came at the expense of her family. She missed one daughter’s wedding and forced the rescheduling of another. She was with her mother when she died but left for a birding trip before the funeral. Her husband had to seal with her extended absences and preoccupation with her notecards when she was at home.

Ironically, Phoebe died in a car crash in Madagascar in 1999 on a birding trip. Cancer never beat her.

[Originally published on May 31, 2009]

Maine River Project; Birds in the News

By in Bird Conservation, Species Accounts

Volunteer Opportunity for Maine Birders

Maine birders and other naturalists have a long history of participation in citizen-science projects. In today’s column, I want to let you know about a new volunteer-based bird project to assess the impact of dams on the birds that use rivers.

Specifically, two dams on the Penobscot River are scheduled for removal in 2011. Volunteers will be sampling the birds of the Penobscot River before and after the removal of the dams.

An essential part of this study will be monitoring control rivers to document any changes in bird abundance over the next few years that are not related to the removal of dams. So rivers like the Kennebec and the Androscoggin need to be monitored as well.

The protocol is straightforward. Each volunteer chooses a section of a river. From a single point, the volunteer monitors birds for twenty minutes, recording the number of birds seen in four consecutive five-minute intervals.

The primary focus is on counting riverine birds that feed on aquatic food resources including cormorants, Bald Eagles, Osprey, waterfowl, herons, shorebirds, gulls, kingfishers, and some songbirds that forage extensively on aquatic insects such as Tree Swallows, Eastern Kingbirds, and Cedar Waxwings. Other species that happen to occur near rivers can be recorded incidentally if you wish.

The river section needs to be surveyed every two weeks during the spring (ice-out until early June) and fall (late August into November) migration periods. Summer counts can be less frequent and winter counts are not essential. Counts should be conducted in the morning.

The project is being led by Erynn Call, a doctoral student in the Department of Wildlife Ecology at the University of Maine. If you are interested in censusing one or more sections of a Maine river, you can contact her by email ([email protected]), letter (Department of Wildlife Ecology, 5755 Nutting Hall , University of Maine, Orono, Maine 04469-5755) or telephone (207-581-2921).

I hope you will consider adopting a section or two of a Maine river for this project. You would be making a valuable contribution to an important project. And, your participation will give you an excuse to go birding!

All About Birds website

The Cornell Laboratory of Ornithology has revised its impressive All about Birds website (http://www.allaboutbirds.org). You can find high-quality images and informative accounts of over 500 bird species. You can listen to vocalizations of many species of birds. Descriptions of favorite birding areas of Lab ornithologists throughout the United States are just a click away.

A brand-new feature is a series of free web videos, called Inside Birding. Two experienced ornithologists, Jessie Barry and Chris Wood, share their tips, tools and techniques for identifying our feathered friends. The first four videos describe their “four keys” to bird identification: size and shape, color pattern, behavior, and habitat. The videos are geared to beginning birders but will be of value to more experienced birders.

Sad News about Whooping Cranes

The Whooping Crane is one of the most endangered bird species in North America. In 1941, the population was only 21 individuals. With a combined effort of habitat preservation, captive breeding and cross-fostering with Sandhill Cranes, the population rose to more than 300 birds in the wild and another 145 in captivity.

One of the world’s two remaining flocks of Whooping Cranes overwinters at the Aransas National Wildlife Refuge in Texas. These birds breed at the Wood Buffalo National Park in northern Alberta.

Last fall, nearly 300 Whooping Cranes departed from Alberta on their migration to Aransas. Unfortunately, 34 of the birds failed to arrive in Texas. Another six adults and 15 chicks did not survive the winter in Texas.

This population of Whooping Cranes therefore lost a fifth of its members over the past six months. Wildlife biologists implicate drought and disease for the deaths of the wintering birds.

Non-Native Purple Swamphen in Florida

In 1996 a family of about six Purple Swamphens were documented for the first time in south Florida. This species is related to the native Purple Gallinule and Common Moorhen that occur naturally in Florida. The swamphen population has exploded since their introduction. Conservation biologists are concerned because the swamphens prey on the eggs and nestlings of native waterbirds and compete for breeding habitat with other marsh birds.

Alarmed, Florida wildlife officials had hunters shoot as many of the swamphens as they could find. This hunting resulted in the extermination of 3,200 birds over a 2.5 year period. This hunting program was not effective and has been discontinued. The Purple Swamphens seem to be firmly established in at least three south Florida counties.

[Originally published on May 15. 2009]

Boreal Song Initiative

By in Uncategorized

Boreal Songbird Initiative – Please help!

The Boreal Songbird Initiative, along with other environmental groups like Bird Studies Canada, Nature Canada, the David Suzuki Foundation, among others created a petition called “Save our Boreal Birds” a little over a year ago. This petition will be sent to the Prime Minister of Canada and many provincial leaders, and asks that vital bird habitat be kept intact despite the fact that over 30% of the Boreal Forest has already been designated for development. Many migratory birds that travel through the US and other countries breed in the Boreal Forest to the north.

Sign the petition at SaveOurBorealBirds.org to protect Canada’s Boreal Forest on behalf of the billions of birds that breed there!

By in Uncategorized

For the Birds – Common Grackle

Chances are good that Common Grackles have returned to your neighborhood by now. These large members of the blackbird family are one of the first of our migratory breeding birds to come back to Maine.

With a sleek, glossy black plumage and a yellow eye, the adult Common Grackle is a striking bird. The birds are about 12 inches long, including the long tail. It is not easy to tell males from females although the head of males, in favorable light, has a glossy purple head and breast. The female is usually slightly smaller than the male. In flight, grackles hold their tails in a V, like the keel of a boat.

Despite their sleek appearance, grackles will win no contests for the beauty of their songs. Both males and females sing the same harsh, squeaky song that some ornithologists interpret as “squ-eek”, “readle-eak” or “scuda-leek”. Some people think the song sounds like the opening of a gate with a rusty hinge. These birds also give a characteristic raspy “chack” call, often in flight.

Males sing more frequently than females and male song rates are highest early in the breeding season. Any individual sings a single song but there is a lot of variation among individuals. The songs therefore seem to be useful for individual identification.

Grackles are habitat generalists. Suburban areas, farmlands, swamps, and orchards are all suitable. Favoring more open habitats, grackles are typically not found in deep forests. Before European settlement and the clearing of forests, Common Grackles were uncommon birds in New England; now they are abundant. Aided by the planting of shelterbelts, Common Grackles have expanded their range westward across the Great Plains.

This species is highly gregarious; if you see one, you will probably see 10. Except for females incubating eggs, grackles roost together at night in noisy roosts, sometimes more than 100 birds in one roost.

Unlike some of our long-distance migrants, Common Grackles do not winter very far to the south of us. Some winter in southern New England with more wintering from Pennsylvania south.

Once the grackles return, keep an eye out for their courtship displays. The male will raise the feathers around his neck, drop his wings and sing his song for a prospective mate. This behavior is called the song spread.

Pairs form soon after the birds arrive. The female builds the nest, usually well above the ground in a conifer. The male guards the female throughout the nest construction process. Once the nest is complete, the female will perform a wing quivering display, a signal that she is ready to mate.

The male aggressively keeps other males away from his mate. A common threat display is sky pointing, when the male raises his bill vertically. This behavior is given by one male on the approach of another male. The display usually results in one of the males departing.

Common Grackles may nest alone but more often in colonies of ten or more pairs in tall trees, especially evergreens. Sometimes, nests are made in freshwater marshes, old building and even the lower parts of Osprey nests. The nest is made of twigs and grass stems. Most nests contain 5-6 eggs, which the female incubates for about 14 days before hatching. The newly hatched birds are ready for their first flight in 14-16 days. Unlike their dark parents, juveniles are dark brown with brown eyes.

Grackles have a broad diet, although insects are the most commonly captured prey. Grackles often search for food on the ground, walking slowly and deliberately. Occasionally, a bird may run and leap into the air to catch an insect. Grackles may probe in the ground for earthworms and will even take them from robins. Grackles will also search for food in trees. Besides insects, grackles are known to eat spiders, snakes, lizards and mice. The eggs and nestlings of other birds are not safe from grackles. Grackles are even reported to wade belly deep in freshwater for crayfishes, minnows, frogs and salamanders. Grackles will eat seeds including corn, acorns, and seeds of various weeds. In fact, Common Grackles are now a major agricultural pest, causing millions of dollars of damage to sprouting corn.

Some Common Grackles attain impressive ages. The oldest known Common Grackle was banded in Michigan and recaptured 20 years and 11 months later in Illinois! A Common Grackle in Minnesota lived to be at least 17 years old while a New Jersey bird lived to be at least 16 years and 1 month old. The average life span is likely much less than these extremes.

[Originally published on April 4, 2009]

By in Uncategorized

For the Birds – Geo-locating and Bird Migration

Keeping track of bird migration is a time-honored practice of naturalists dating back over 200 years. All of us delight at the arrival of the first Red-winged Blackbirds, Hermit Thrushes, or Yellow Warbler in the spring.

Until recently, our understanding of the timing of bird migration was based on populations of birds rather than individuals. We have to be able to follow individual birds to truly understand migration speeds and routes.

Bird banding has contributed some useful information. However, the chance of a bird bander capturing a bird banded earlier in the migration is pretty slim. The chance of capturing a banded bird immediately after its arrival is slimmer yet.

Outfitting birds with radio-tags that emit unique frequencies provides a way to track individual birds. The range of most radio-tags is limited to a couple of miles so this technology is more useful for tracking the movements of resident birds.

More recently, satellite transmitters have been developed that allow ornithologists to monitor the position of birds from their computers. For instance, researchers used satellite transmitters to track the migration of Short-tailed Albatrosses across the Pacific Ocean (http://www.wfu.edu/biology/albatross/shorttail/shorttail.htm).

Although radio and satellite transmitters have been miniaturized, they are still too large to place on most songbirds. A new technology, called geo-locating, promises to provide new insight into the pace and direction of small bird migration.

The geo-locaters were engineered by members of the British Antarctic Survey for use on larger birds and later miniaturized for use with songbirds. The songbird geo-locators are light (0.05 ounce). The device is essentially a small computer chip with a built-in clock and a short stalk. The geo-locator tracks light levels so that sunrise and sunset are recorded for each day. Knowing sunrise, sunset and day length allows the researchers to precisely determine the position of the bird every day. Essentially, the length of the day allows the latitude to be determined and the time of sunrise and sunset allows the longitude to be determined. Pretty neat!

The geo-locater is held on the rump of the bird with straps that wrap around the upper part of each leg.

The first results of this technique were recently published by a team of researchers led by Bridget Stutchbury from York University. The team captured 20 Purple Martins and 14 Wood Thrushes in the fall of 2007 in northern Pennsylvania. They were able to recapture five of the Wood Thrushes and two of the Purple Martins in the spring of 2008. The researchers downloaded the data from the geo-locater and were able to map the fall migration, winter movements and spring migration of each bird.

Even though only seven birds were recaptured, the results already cause us to rethink how migration occurs in songbirds. In the fall, the two Purple Martins flew south to the Yucatan Peninsula in five days (about 1500 miles in total). The martins stopped there for three to four weeks before continuing their migration to a wintering area to Brazil.

We know that spring migration is typically much faster than fall migration in most birds. There is an urgency about the spring migration as birds stream north to find mates and favorable territories. However, the speed of the Purple Martin spring migration was more rapid than suspected. One of the tagged martins flew from the Amazon basin back to Pennsylvania in only 13 days, traversing over 3000 miles. Four of those days were spent on stopover. Prior to this work, ornithologists believed that a nightly flight of about 100 miles was about the maximum distance most songbirds can manage.

Four of the five Wood Thrushes migrated to the southeastern United States, spending one to two weeks there before flying across the Gulf of Mexico to the Yucatan Peninsula. The birds wintered in Honduras and Nicaragua. Most of the thrushes returned to Pennsylvania in 13 to 15 days, again crossing the Gulf of Mexico. One thrush took the landward route, avoiding the Gulf crossing.

[Originally published on March 21, 2009]

By in Uncategorized

For the Birds – Costa Rica Trip – Part II

This column is the second of two presenting some birding highlights of my visit to Costa Rica in January.

We left the rainforest reserve at La Selva bound for the Ecolodge at San Luis just west of the Continental Divide. The trade winds were unrelenting there, making birding by ear difficult and keeping the birds down.

One of the highlights was a pair of Emerald Toucanets, a mostly green small toucan. A pair of male Black-breasted Wood-Quail were fighting with other, oblivious to the ten people watching them.

In local pastures, I had nice views of Yellow-faced Grassquits, White-eared Ground-sparrows and a Social Flycatcher. Raucous Brown Jays were extremely common.

A local family maintained a bird feeder, stocked with fruit, that attracted Blue-gray Tanagers, Passerini’s Tanagers, Crimson-collared Tanagers (spectacular!), Buff-throated Saltators and Yellow-throated Euphonias. Old friends were seen in the trees: Black-and-White Warbler, Chestnut-sided Warbler and Baltimore Oriole.

We hired a taxi to take us from San Luis to the Monteverde Cloud Forest Reserve for a daylong adventure. This site was only 500 meters higher than San Luis but was truly a different world. Typical weather is misting rain with low-lying clouds. Epiphytes are everywhere on the trees.

The most sought-after bird at Monteverde is the Resplendent Quetzal, a specialist on avocados. We hired three guides to lead our class on a morning walk. The guides knew of an avocado tree where a pair of quetzals were feeding. With patience, we got a good look at a female through a spotting scope. Later in the morning, a male appeared briefly no more than 50 feet way.

The Resplendent Quetzal, a member of the trogon family, is often touted as the most beautiful bird in the world. I find it hard to argue. The male has a brilliant green head, throat and back and a scarlet red breast and belly. The tail is white with four long green uppertail coverts that extend well beyond the tail. The female is similar with more muted colors. Females lack the long tail coverts of the males.

This species is the national bird of Guatemala. Quetzals were revered by the Aztecs, Mayas and other Mesoamerican peoples.
Other avian highlights at Monteverde included a Black Guan, a roosting Mottled Owl, and Ochraceous Wood-Wrens. Several fearless Slate-throated Redstarts flitted about us for a while. These mostly yellow sprites are called candelitos (little candles) by Costa Ricans because their frenetic movements suggest flickering.

We saw seven hummingbird species including the large Green Hermit and Violet Sabrewing. Stripe-tailed Hummingbirds were seen as well. These hummers are nectar robbers. Many flowers with long tubular flowers rely on hummingbirds for pollination. The flowers essentially reward the hummingbirds with nectar for acting as pollinators. Striped-tailed Hummingbirds have relatively short bills. To reach the nectar of tubular flowers, the birds pierce the base of the flower to get the nectar but do not get a shower of pollen on them like other hummingbirds do.

Bananaquits and Common Bush Tanagers were nice finds as well.
Our last stop was the tropical dry forest of Santa Rosa National Park. This park is in the northwest corner of Costa Rica. We were there during the dry season when a strong rain shadow effect of the mountains to the east makes rain a rare event for half of the year. It was very hot during our stay.

Because of the dryness, some of the trees lose their leaves. The forest floor had a significant layer of dead leaves, similar to our northern broad-leaf forests.

The most conspicuous birds were White-breasted Magpie-Jays with their curly feathers on the top of the head. A Roadside Hawk, a buteo hawk, was regularly seen. Three species of parrots were heard and sometimes seen: White-fronted Parrot, Yellow-naped Parrot and Orange-fronted Parakeet.

Hoffman’s Woodpecker was the most common woodpecker. Flycatchers were conspicuous but less diverse than at La Selva. Most were Great-crested Flycatchers, Dusky-capped Flycatchers and Streaked Flycatchers
The resident Rufous-capped Warblers were joined by Yellow Warblers.

The pigeons were represented by three common species: Inca Dove, White-tipped Dove, and White-winged Pigeon.  Thicket Tinamous called from sights unseen. Lots of Ruby-throated Hummingbirds were present. Other neat birds were Barred Antshrikes, Rufous-naped Wrens and Scrub Euphonias. We found a sleeping Northern Potoo, doing a superb imitation of a broken tree limb.
Santa Rosa is a great place to see monkeys. We had several extended views of white-faced capuchin monkeys and howler monkeys.

A trip to the Pacific Ocean (Playa Naranjo) yielded Brown Pelicans, Magnificent Frigatebirds and lots of Brown Boobies. I never got used to the lack of gulls.

[Originally published on March 7, 2009]

By in Uncategorized

For the Birds – Costa Rica Trip – Part I

My colleague Judy Stone and I spent most of January in Costa Rica teaching a Colby biology class. The focus of our course was plants of the tropics but I had time to enjoy some wonderful birding while we were there. I’ll devote this column and the next to some of the birding highlights of our visit.

Costa Rica is a small country, roughly the size of West Virginia. Within that small area, however, the range of climate, topography and vegetation is great. It is no wonder that 875 species of birds occur in Costa Rica. The United States and Canada combined scarcely exceed that number of species.

We spent our first week in Costa Rica at the La Selva Biological Station near the town of Puerto Viejo, north of San Jose. This site, at an elevation, of about 500 feet is lowland rainforest. The trade winds blow across Costa Rica from the east, bringing moisture-laden air off the Caribbean onto shore. As the air rises, it cools and drops the moisture as rain. We were at La Selva during the dry season but, as we learned, La Selva has a rainy season and a rainier season. We were lucky though as most of the rain fell during the evening hours.

The first bird I saw at La Selva looked like a small warbler, flitting near the top of a large tree. It was a warbler indeed but not the tropical species I was expecting. It was a Chestnut-sided Warbler, one of the most common nesting warblers in Maine. I noted a number of other birds that breed here in Maine enjoying the Costa Rican warmth: Turkey Vulture, Tennessee Warbler, Louisiana Waterthrush, Baltimore Oriole and Red-winged Blackbird.

We were assigned rooms in an older building called the River Station, overlooking the Puerto Viejo River. A pair of Crested Guans, chicken-like birds with bright red wattles, were feeding just above the trail on fruits. A Blue-black Grosbeak was in an adjacent tree.

Montezuma’s Oropendolas were the most conspicuous birds at La Selva. These members of the blackbird family are large and loud. Males are about 20 inches long, females five inches shorter. Most black, Montezuma’s Oropendolas have bright yellow tails and conspicuous white markings on the side of the head. Females were just beginning to build their pendant nests in palm trees. The nests are similar to those of a Baltimore Oriole but much longer. Males were displaying to females. The display is memorable. The male perches on a branch and gives a loud, liquid song. At a distance, the song is quite pleasing but metallic screeches can be heard when close to a male. As the male finishes his song, he performs a deep bow, rotating his body a full half turn, showing off his bright yellow tail. Despite the bravura performances, the females seemed unimpressed.

Mornings at La Selva were almost magical. Great Tinamous gave their wavering, flute-like call from deep in the jungle. Rufous Motmots gave their lovely hoot-hoot-hoot calls that reminded me of notes from a wooden percussion instrument. As dawn approached, the glorious songs of White-breasted Wood Wrens, Striped-breasted Wrens and Black-throated Wrens filled the air.

Parrots were vocal but usually difficult to see in the tops of trees. With patience, we got good looks at Mealy Parrots, Red-lored Parrots, Brown-hooded Parrots and White-crowned Parrots. The highlight though was eight fly-over Great Green Macaws. Only about 200 individuals are left in Costa Rica.

Birds at La Selva often move in large, fast-moving mixed flocks. One memorable flock had Palm Tanagers, Passerini’s Tanagers, Dusky-faced Tanagers, Blue-gray Tanagers and Golden-hooded Tanagers. Within five minutes, the flock had moved on.

I enjoyed seeing birds in families that were new to me. A Rufous-tailed Jacamar, related to the woodpeckers, looked alike an overgrown hummingbird with its long thin bill. A pair of Pied Puffbirds provided us with great views; these birds are also related to the woodpeckers. We saw Northern Barred Woodcreepers and Streak-headed Woodcreepers. Woodcreepers are perching birds that behave much like woodpeckers. A Great Antshrike gave me a brief look before diving back into its preferred dense undergrowth habitat.

Other memorable sightings included a male Green Honeycreeper with fluorescent green plumage, Olive-backed Euphonias, a Green Kingfisher and a ton of flycatcher species including Boat-billed Flycatcher, White-ringed Flycatcher, Common Tody-Flycatcher, Mistletoe Tyrannulet, Rufous Mourner, Bright-rumped Attila and Long-tailed Tyrant. Chestnut-colored Woodpeckers, Black-cheeked Woodpeckers and Pale-billed Woodpeckers were striking birds as well.

[Originally published on February 21, 2009]

By in Uncategorized

For the Birds: Maine Christmas Bird Count review

The Maine Christmas Bird Counts conducted from Dec. 14 to Jan. 5 yielded particularly high numbers of sightings of common species, of irruptive species like Bohemian waxwings – and of the rarities whose discovery makes a Christmas Count so exciting.

Perhaps the most remarkable species in this winter’s count are the pine siskin and white-winged crossbill. Both are irruptive species, visiting Maine in the winter when their food supplies are depleted to our north.

The pine siskin irruption this year has been nothing short of spectacular. These wanderers have been absent from many Maine Christmas Bird Counts over the past decade. Consider the sightings from this year’s counts: 92 in Augusta, 297 in the Belfast area, 361 in Waterville and 350 in Biddeford-Kennebunkport.

Interestingly, pine siskin numbers were quite low on counts dominated by spruce-fir forest that normally have the highest numbers of these sprites. The Misery township (just south of Jackman) and the Schoodic Peninsula counts yielded only four.

The number of pine siskins sighted in Maine has continued to increase over the past month. Peter Vickery of Richmond saw a Eurasian siskin among the pine siskins at his feeder. Get your niger seeds out there for the siskins!

White-winged crossbills have also staged an impressive invasion this winter. Many counts shattered their previous records for this species. The Portland counters found 672 white-winged crossbills – the previous record was eight. Similarly, the Waterville count produced 216, dwarfing the previous high of five.

The Misery count usually produces the most white-winged crossbill sightings, but this year none were found there. I saw lots of white-winged crossbills this summer in coastal Washington County, but none were found in the Moose Island-Jonesport count. The crossbills seemed to have pushed south of their typical winter range.

Common redpolls generally show a biennial pattern of irruption into Maine. Last year, these birds staged a major invasion into the state. One therefore expects this winter to have a light flight of these finches.

Although a number of counts recorded redpolls, numbers were usually low except for the 147 in the Augusta count.

As is typical, Bohemian waxwings had a patchy distribution in Maine over the count period. The Bangor-Bucksport count produced 1,794 Bohemians (and 792 cedar waxwings) and 670 were in the Farmington count. Elsewhere, Bohemians were mostly absent, or present in single digits.

Red-bellied woodpeckers staged a strong invasion into Maine this fall, and a number of them were found by Christmas count participants. The Portland count had 15 red-bellies, eclipsing the former record of four. Six were found in Bangor-Bucksport, eight were found in Augusta and 17 in Biddeford-Kennebunkport.

Blue jays show an intriguing winter movement called partial migration. Some blue jays spend the entire year in Maine, while a proportion will migrate to more southerly areas, particularly if food supplies are low. Blue jays depend heavily on acorns during the winter. The acorn crop must have been more than adequate this year as higher than normal numbers of blue jays were counted in many Maine counts. In Augusta, the 674 blue jays shattered the previous high count of 61.

Maine Christmas Counts usually yield a number of lingering birds that will likely be forced to migrate or perish before the winter is over. Great blue herons are a case in point. Hardy herons showed up on the Biddeford-Kennebunkport, Portland, Thomaston-Rockland, Waterville, Augusta, Moose Island-Jonesport and the Schoodic Peninsula counts.

Other lingering species included a common tern, Eastern bluebirds, hermit thrushes, Carolina wrens, yellow-rumped warblers, a yellow-breasted chat, a summer tanager, Eastern towhees, fox sparrows, a white-crowned sparrow, a grasshopper sparrow and a Baltimore oriole.

Not surprisingly, most of these showed up on counts in the southern part of the state, especially along the coast where the weather is not quite as severe as in northern and inland areas.

As usual, the Portland count recorded the highest number of species in the state. The 114 species tallied represent a new record for the count. Four species were found that had never been recorded on that count: ruddy turnstone, blue-headed vireo, clay-colored sparrow and red crossbill.

As expected, the Misery count yielded the lowest number of species in this challenging environment. Fifteen species were counted, including gray jays, pine grosbeaks and red crossbills.

To see the complete totals for the Maine Christmas Bird Counts, visit www.audubon.org/Bird/cbc

[Originally published on February 7, 2009]

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