November 2016

Northern Finches

By in Foraging, Migration

Are they coming this winter or not?  One hears this question a lot in birding circles at this time of year.  The question centers on the group of birds called the northern finches or winter finches, higher-latitude birds that grace us with their presence in some winters but not in all.  The only predictable feature of northern finch abundance is unpredictability.

The northern finches include Purple Finch, Pine Siskin, Evening Grosbeak, Pine Grosbeak, White-winged Crossbill, Red Crossbill and Common Redpoll.  Although some of these species nest in Maine, most individuals of these species nest well to our north.

All of these species depend on the seeds from trees for their sustenance, particularly during the winter. Redpolls are fond of birch seeds and the rest specialize on conifer seeds (firs, hemlocks, spruces, larches and pines).  Pine Grosbeaks have a taste for fruit as well.

When seed abundance is adequate on the breeding grounds, these finches will forgo a southern migration and spend the winter on their breeding grounds.  The birds spare themselves from the significant cost of migration. However, seed production by the trees the finches depend on varies dramatically from year to year. In a year of low seed production, the northern finches are forced to be nomads, wandering south until they encounter the seeds they need.

These southern migrations are called irruptions.  The birds irrupt or move into areas away from their breeding grounds.

In our neck of the woods, three conditions have to arise for us to see an irruption of Common Redpolls, White-winged Crossbills or other irruptive species. First, seed production on the finches’ breeding areas has to fail. Second, seed production of those trees has to be high in Maine. Third, the irruptive finches have to happen upon our abundant seeds in their wanderings.

For the past 20 years or so, Ron Pittaway in Ontario has been putting out a winter finch forecast.  He gathers data on the cone production of various conifers, birch and fruit trees.  He has been remarkably good in predicting flights of irruptive finches.  His data for southern Ontario mirror abundances in neighboring provinces and states.

According to Pittaway, this winter will likely be poor in Maine for Pine Grosbeaks. Mountain Ash in the boreal forest produced many berries this summer.  Pine Grosbeaks will have no need to irrupt.

On the other hand, cone production by several species of conifers across the boreal forest was modest at best.  Pittaway expects White-winged Crossbills, Red Crossbills and Pine Siskins to stage irruptions.  Purple Finches have already started to appear in Maine in good numbers at feeders.

The Evening Grosbeak has had a couple of excellent breeding years so their population seems to be on a bit of an upswing after several decades of declines.  Pittaway thinks these birds are likely to be seen at feeders in southern Ontario and northern New England.

So far, he seems right on the money.  In the past week or so, I have heard reports of Evening Grosbeaks in Machias (100 birds!), Newcastle, Bangor, Wells, Skowhegan, Gardiner, Milbridge, Pittsfield, Biddeford, and Yarmouth.  You get the picture; it is an irruption!  I am not alone in hoping we have an abundance of these beautiful finches here all winter.  Keep those sunflower feeders filled.

Red-breasted Nuthatches depend on conifer seeds during the winter as well. Unsurprisingly, their irruptions tend to coincide with those of Purple Finches, Pine Siskins and White-winged Crossbills.  I’ve seen more Red-breasted Nuthatches this fall than I have in the past few years.

Blue Jays also show irruptive behavior, responding to the abundance of their preferred winter food, acorns. Acorn production has been low this year in central Maine, perhaps due to the dry summer we had.  Many of our Blue Jays will move south for the winter.

[First published in mid-November, 2016]

Listing and Competitive Birding

By in Birding and Birders

Grocery lists, to-do lists, bucket lists.  Making lists is a common human behavior.  Birders engage in this practice, keeping lists of birds seen on trips or birds seen at their feeders.  But the most common such list is the life list, a compendium of all the species of birds one has seen in one’s lifetime.

Some birders keep a life list but don’t even bother to count how many species are on their list. Others keep close track but keep their totals to themselves. Yet others are interested in publishing their list totals and comparing their lists to others.

Let’s step back in time to 1970. Jim Tucker of Texas had envisioned a birding publication that would focus on the publication of top species lists for different areas, identification tips for hard-to-identify birds and descriptions of sites where rare species might be seen. The first issue of his brain-child, Birding, was published in February, 1970 and soon thereafter the American Birding Association (ABA) was created with Birding as its flagship journal. The early members of the ABA thought Birding should not contain articles on ornithological research or on conservation efforts but rather should fill a perceived void for competitive birders and birding hobbyists.  Thus, a formal mechanism for competitive listing began.  Birders submitted their list totals and could see how they stacked up against other birders. The game was on!

The ABA has thousands of members now.  The mission has expanded considerably to cover avian conservation, book reviews and ornithological history. However, maintaining members’ list totals is still a mainstay of the organization.

You can check out list totals at the Listing Central page on the ABA website (http://listing.aba.org/). For Maine, the top lifetime lister is Doug Hitchcox with 374 species seen.  The top year list for Maine (the total birds seen in a calendar year) is also Doug Hitchcox for his 2011 effort.  Frank Paul has the largest life list for Cumberland County.

Keep in mind that not all birders submit lists to ABA Listing Central. The popular eBird site (http://tinyurl.com/c8atyh) has the capacity to generate lists at different geographic levels and for different time intervals. I see that Pat Moynahan has a Maine life list of 380 species. I know there is at least one other birder in Maine whose lists do not appear in the ABA or the eBird database who has seen even more species in Maine.  Some top listers simply choose to not play the game.

I’ve been thinking about listing lately because of the success of four birders who are doing a Big Year in North America. These hard-core birders are traversing the continent to try to surpass the total of 749 species seen in 2013 by Neil Hayward.

Completing a successful Big Year requires finding all of the 671 species that occur regularly and widely in North America.  One must target another 82 species that occur in North America each year but are rare.  Finally, one has to make trips to places like the Aleutian Islands, southern Texas and southeastern Arizona to find vagrants.  The time and money to be able to jump on a plane at a moment’s notice to see a rare bird is essential.

It turns out that 2016 has been a phenomenal year for rarities. Four birders have broken the 700 species mark, the first time that has ever happened in a calendar year. Furthermore, the record of 749 species was shattered in July!  John Wiegel, an Australian, saw a Buller’s Shearwater on July 16 for his 750th species. Olaf Danielson, a physician from South Dakota, racked up his 750th with a Red-faced Cormorant in Alaska. Currently, Wiegel is in the lead with 770 species to Danielson’s 765. Wow!

Laura Keene has found 737 species to date, besting the prior women’s record. Finally, Christian Hagenlocher has tallied 734 species.

Swainson’s Hawk in Millinocket!

By in Foraging, Identification, Insects, Migration, Species Accounts

On September 29, Rhonda Little-Aifa posted photographs of an unfamiliar hawk on the Maine Birds Facebook page.  The bird was at the Millinocket Airport on Medway Road, first seen a few days earlier.

Doug Hitchcox, the Naturalist at the Maine Audubon Society, recognized the bird as a Swainson’s Hawk.  Swainson’s Hawks nest on cliffs near grasslands in western North America and spend the winter in South America, as far south as Argentina.

Clearly, this was a bird out of place.  The Maine Birds Checklist Committee recognizes only two prior records for the state, one seen on May 3, 2009 in Pownal and on seen on September 23, 2013 in Harpswell.  Eight other reports of this species, dating from 1883 to 2005, have not yet been reviewed by the Checklist Committee.

A major migration of birders to Millinocket began on September 30. Dozens of birders got to see this cooperative bird, particularly over the weekend.  The hawk was last soon on the morning of October 4.  You can see pictures at: http://ebird.org/ebird/view/checklist/S31826769

Swainson’s Hawk belongs to the genus Buteo, the genus that also includes the familiar Red-tailed Hawk and Broad-winged Hawk.  Swainson’s has proportionally longer wings and a smaller bill than the similarly-sized Red-tailed Hawk.

Swainson’s Hawk has colloquial names of locust hawk and grasshopper hawk.  The hawks feed often on the ground, chasing grasshoppers, a favored food.  The Millinocket Bird spent most of  its time perched on the fence surrounding the airport or walking/running on the ground, chasing down grasshoppers. Louis Bevier made a video of the hawk capturing a grasshopper: You can watch the video at: https://vimeo.com/185072912

Swainson’s Hawks will also catch dragonflies and other large insects on the wing.

Normally, Swainson’s Hawks migrate south from their western breeding grounds, through Central America and then spread out in South America. Like most Buteo hawks, Swainson’s Hawks are averse to migrating over water.

Swainson’s Hawks are one of the most abundant species migrating through the Isthmus of Panama. Hawk watchers in Panama City counted 900,000 soaring migrants (mostly Swainson’s Hawks and Turkey Vultures) passing overhead on a single day in November of 2013.  That record was eclipsed on November 2, 2014 when 2.1 million birds passed over.  What a spectacle that must have been!

This hawk joins a long list of vagrants to Maine from western North America.  These birds include White-winged Dove, Western Flycatcher, Calliope Hummingbird, Hermit Warbler, Brewer’s Sparrow, Black-throated Sparrow and Western Meadowlark.

I think it is significant the the Millinocket Swainson’s Hawk was a young bird, born in the summer of this year.  Many birds that appear in unexpected places during migrations are naïve, inexperienced birds.  Young birds are much more likely to make navigational errors than more experienced birds.

Navigation during migration involves two abilities. Most migrants are capable of vector navigation, maintaining a particular compass direction for a specified length of time or distance.  True navigation requires that a bird knows exactly where it is, even if it is displaced by a storm or wind.

Experiments demonstrate differences between the navigational abilites of juvenile and adult birds. Imagine Yellow-rumped Warlers banded on their breeding grounds in Maine that normally would migrate south to North Caroina for the winter. Vector navigation in a south-southwest trajectory will get those birds to their wintering grounds.

Some ornithologists have experimentally captured such birds and displaced them eastward or westward.  Let’s fly some warblers from Maine to Minnesota and release them there in the fall.  Adult birds have true navigation; they realize where their displaced position is and will migrate in a southeasterly direction to get to North Carolina.  The young warblers are poor at true navigation.  Most will use their vector navigation skills and head south toward Texas. Vagrant birds therefore tend to be young birds that are much more likely to get lost.

Fall Migration Tips – II

By in Migration, Weather

In the last column, I provided some tips on how to predict when migrating birds are likely to be seen in your local patch. Experiencing a fall-out of migrants is exhilarating. In today’s column, we will explore ways that you can experience migrating birds while they are in flight.

Some birds migrate during the day.  We have all thrilled to skeins of Canada Geese or Double-crested Cormorants, winging their way in V-formation to more favorable areas.  Hawks, eagles and falcons are diurnal migrants as well.  They are adept at taking advantage of the vertical winds, called thermals, that form during the day due to uneven heating of the earth’s surface. A rocky outcrop will warm more rapidly than an adjacent forest. The rocks warm the air, the air rises and is replaced by cooler air from the adjacent forest.  That cool air warms, rises and you get the picture.  Hawks are masters at soaring from thermal to thermal, scarcely beating a wing.

A sunny day with winds in the right direction produces spectacular numbers of these soaring migrants.  Mt. Agamenticus in the Ogunquit area and Cadillac Mountain in Acadia National Park have several thousand raptors migrating over them each fall.  Bradbury Mountain in Pownal can be great for spring hawk migrants.

Hawk watching is a boom-or-bust activity.  Make sure the weather conditions are right and you may be rewarded with more hawks than you can follow.

Shorebirds and most of our songbirds are nocturnal migrants.  Advantages of night-time migration are three-fold. The risk of predation from raptors is low. The air is cooler; migrating birds raise their metabolic rate so high they must constantly dump heat or they will overheat. The cooler air helps them balance their heat budget. Finally, the air is less turbulent at night, making powered flight more efficient.

Migrating songbirds mostly migrate at altitudes of 2,000 to 4,000 feet. Shorebirds may fly a bit higher.

How can you see these birds at night? Get your binoculars or, better yet, a spotting scope and train it on the surface of the moon. If migration is occurring, you will see the silhouettes of birds passing in front of the moon’s image.  Don’t expect to see birds flying at their normal migrating height but as birds take off or descend, they are easily seen against the moon.  The technique works well for birds that are no more than several hundred feet above the surface of the earth.

You can also appreciate migrating birds at night from radar images. In the early days of modern radar in the early 1940s, mysterious blips were detected on radar screens. They proved to be no threat to military aircraft.  These echoes were called angels.  Now we know that the angels are small flocks of birds.

The Doppler radar used now for weather forecasting is perfect for detecting bird migration.  Here is the URL for a great tutorial on how to use the freely available NEXRAD radar images to monitor migration: http://www.woodcreeper.com/videos/NCAR_Tutorial-desktop.m4v

Yet one more way to appreciate nocturnal migration is to use your ears.  Nocturnal migrants are noisy, regularly emitting short flight notes.  In some cases, the flight notes are similar to the calls the birds give while they are on the ground.  In many cases, however, the flight notes are only given during a nocturnal flight.

Bill Evans has been a pioneer in the study of nocturnal flight calls.  Visit his website at  http://www.oldbird.org/ He has sonograms for a number of warblers and sparrows.

On a night that is not too windy, you can hear the flight notes above.  However, a microphone will capture many more of those vocalizations.  Evans provides directions on how to build a microphone system using cheap materials like a plastic flowerpot, saran wrap, a dinner plate and an inexpensive microphone.

Fall Migration Tips – I

By in Migration, Weather

The southward migration of five billion birds in North America is a staggering phenomenon.  These migratory movements provide us with the chance to see a diversity of birds, often in very high numbers.  I will devote the next columns to ways to fully experience the fall migration.

Migrating birds are flying right on the edge of survival.  Flight is energetically taxing, requiring that a bird’s metabolic rate be raised five times or more above its resting rate.  With the exception of birds like swallows, swifts and kites that feed on insects on the wing, migrating birds cannot refuel during flight. One way migrating birds try to maximize the length of a migratory leg is to take advantage of favorable winds.

A weather map offers you a tool to predict when migrations will be strong by looking at the relationship of low- and high-pressure systems.  Generally, high-pressure systems alternate with low-pressure systems, moving from west to east across the continent.

A high-pressure system has winds that circle the center of the system in a clockwise pattern.  The leading edge of the high-pressure system therefore has winds that flow from north to south.

A low-pressure system has winds that flow counterclockwise.  The winds on the backside of a low flow to the south.

To determine when conditions are perfect for a wave of fall migrants, all you have to do is find the nearest cold front (indicated on the weather map by a line with triangles).  At the cold front, an area of cool air from a high-pressure system moves underneath the less dense, warmer air of the low-pressure system.  The rising air cools, usually causing a line of precipitation.

As the front passes, a strong flow of wind blowing to the south occurs with the interaction of the trailing edge of the low-pressure system and the leading edge of the high-pressure system.  Depending on the rate at which the high-pressure system moves, spectacular migrations may be seen for several days.

If you see a warm front passing across your neighborhood, you do not need to worry about getting up at the crack of dawn to look for migrating warblers or sparrows.  A warm front (indicated by a line with semicircles on your weather map) is caused when a low-pressure system slides over and above a high-pressure system.  In this case, the winds at and behind the front will flow to the north.  Birds migrate mostly when the winds are favorable and will stay put if the winds are opposite their migratory trajectory.

On a favorable night, birds will fly as long as they can, settling down sometime in the wee hours of the morning.  Sometimes, precipitation can cause birds to land en masse.  By luck, a given spot may be hopping with birds.

Where is the best place to look for a fallout? Frankly, serendipity plays a huge role here. Sometime fallouts are broad, occurring over a county-sized area; at other times, the fallouts may be quite restricted.

However, some places are more likely to produce fallouts.  Shrubby areas along the immediate coast are often productive. Birds that are migrating just offshore will seek landfall to rest and refuel. A dawn excursion to a coastal area can produce a stream of tired birds, welcomed by dry land.  Fort Foster in Kittery, Two Lights State Park in Scarborough and the Eastern Promenade in Portland often harbor many fall migrants.  I have experienced fallouts at West Quoddy State Park in Lubec.  Any patch of coastal real estate with some bush and tree cover can be productive.

Migrating birds may look for islands of habitat in areas that are heavily developed.  The Evergreen Cemetery in Portland is one such magnet.

Finally, migrants need water so checking ponds, streams and rivers can produce excellent fall migrant numbers.

Fall Migration

By in Foraging, Identification, Migration

It’s late Augusts and the fall migration is well underway.  Where did the summer go?

Migrations are tremendously expensive undertakings for birds.  They must pack on fat to fuel each leg of their long journey.  To see fall migratory birds, finding an abundant food source is a good strategy.  Putting on fat quickly is an imperative for migrating birds so they know the best places to eat.

My wife and I spend a lot of time in Lubec on Cobscook Bay.  The area is a wonderful birding destination with lots of accessible conserved land.  During the fall migration, my wife and I use the strategy of going to the food to find the birds.  If you want to see diners, go to a restaurant.

The South Lubec Sand Bar can be hopping with shorebirds and other water birds from August into October.  This bar is about a mile long and is adjacent to an expansive sandflat along the South Lubec Road.  This sandflat is the best restaurant in the area for sandpipers and plovers.

Sandpipers forage by rapidly probing into the sediment, capturing invertebrates by feel.  Their bills are well equipped with touch receptors.  The sandpipers prey on small shrimp-like crustaceans called Corophium as well as polychaete worms, marine relatives of earthworms.  These invertebrates are found in the lower to middle part of the intertidal zone.

Plovers use a different feeding technique, relying more on their vision than their touch.  A plover stands and looks for movement in the sediment. The plover then runs to that unsuspecting prey animal and captures the ragworm, bloodworm or other invertebrate.  This form of feeding is called ambush predation or run-and-peck predation.

The plovers and the sandpipers are dispersed broadly across the flat at low tide. Birding at this stage of the tide is fruitless.

The trick is to let the rising tide bring the birds to you. As the tide starts to cover the productive part of the flat, the birds seem to redouble their feeding efforts as they are forced higher and higher in the intertidal zone.  They congregate right along the rising tide line, seemingly oblivious of the humans staring at them.

For an hour or so, large number of shorebirds will be congregated in a narrow swath, affording great views. Eventually, the tide will force the birds to higher ground.  The birds fly off to local fields or other open habitats and the show is over.

I have found that arriving at the sand bar four hours before predicted high tide is optimal.  The birds will start congregating within the next hour.  By two hours before high tide, the birds will have gone to roost.

Of course, it is possible to arrive at high tide and wait for the birds to return.  I have had less success with this method as the birds seem to be more aware of human presence.

We walked the sandbar recently with a group of friends. Diversity and numbers of birds varies from day to day.  We had a corker of a day but not high bird diversity.  We enjoyed stunning close-up views of many Least and Semipalmated Sandpipers. The Leasts with their reddish-brown upperparts and yellow-green legs are lovely birds.

We had fun picking out the occasional White-rumped Sandpiper from the flocks.  These birds are easy to identify in flight by their namesake white rump.  On the ground, they are similar in color to the gray Semipalmated Sandpipers but a bit larger.  The tail of a White-rump extends well beyond the folded wings, unlike the shorter tail of Semipalmated Sandpipers.

A few Semipalmated Plovers and Greater Yellowlegs rounded out our list for the day. We often see a Merlin, Peregrine Falcon and even a Parasitic Jaeger hunting the shorebirds but not that day.

Of course this technique of letting the tide bring the shorebirds to you works on any intertidal mudflat. Give it a try!

 

House Sparrows – II

By in Behavior, Reproduction, Species Accounts

In the last column, we explored the biology of House Sparrows.  This species is dependent on human-altered landscapes for their existence. The abundance of House Sparrows and their tolerance of human proximity make House Sparrows excellent subjects for ornithological research.  In today’s column, I will review some of the research on these birds.

House Sparrows can change habitat preferences quickly. Introduced into eastern North American 1n 1851, House Sparrows were most common in cities.  Until the turn of the 20th century, urban areas where perfect for House Sparrows. Horses provided the major means of human transportation and the hay to feed to horses had plenty of seeds to satisfy the cravings of House Sparrows.  Many seeds pass through a horse gut intact so horse droppings provided good foraging as well.

As automobiles replaced horses in cities, House Sparrow abundance in cities declined and the birds shifted their preference for agricultural landscapes. The primary food of most House Sparrows is now cereal grains like wheat, corn and oats.  Some Argentinian House Sparrows make ends meet in urban environments by feeding on the nectar produced by aloe plants in public parks.

House Sparrows have provided a test of Bergmann’s Rule.  This rule states that the size of members of a species (or related species) should increase as one goes from the equator to the poles.

The reason is related to the challenges of maintaining a constant body temperature at colder temperatures. A larger animal has a lower surface to volume ratio.  Heat is lost across the surface of an animal but produced by all the cells in the body, hence proportional to volume. In seasonal environments where food abundance is highly variable, a larger animal will be able to tolerate lack of food longer than a smaller animal.

Studies of the geographic variation in size of House Sparrows in North America provide support for Bergmann’s Rule.  From an initial introduction, House Sparrows have spread broadly throughout North America.  Size is negatively correlated with average January temperatures and size is positive correlated with latitude.  In Europe, the pattern is murky. No strong pattern of increase in size occurs with increasing latitude.  More work is needed.

Male House Sparrows have a black bib.  Animal behaviorists call such a feature a badge.  The extent of the black is an advertisement for the quality of the male; females choose a mate, at least in part, based on the size of his badge.

We know that males with larger birds acquire a mate earlier than small-badged males.  Large-badged birds also usually have superior nesting territories.

We think of House Sparrows as monogamous birds. From DNA fingerprinting, we know that cheating on a spouse is common in House Sparrow communities. About 20% of nestlings are sired by a male other than the female’s mate.

Research in Sweden indicates that large-badged males are received more frequently in extra-pair dalliances than small-badged males.  The tables can be turned.  The mate of a large-badged male is often cheated on by his mate.

Some House Sparrows in New Zealand are clever birds indeed.  In Hamilton, House Sparrows fly into the bus station when the automatic glass doors slide open, activated by an electric eye. The House Sparrows find plenty of food to eat from the crumbs that humans drop from their breakfasts and lunches purchased inside.  The Hamiltonians are very tolerant of the scavenging House Sparrows.

A hungry House Sparrow needs to wait for a human to enter or exit the bus station so the doors slide open.  However, some House Sparrows have figured out they can perch on top of the small metal box above the door that houses the electric eye.  The birds lower their head to break the laser beam and, voila, the door opens when the sparrows want to get in.

House Sparrows – I

By in Species Accounts

I’ve just returned from a late July meeting in Miami.  Alas, I had no free time to go birding but I certainly saw many Rock Pigeons and House Sparrows.  One expects to see these two species in any urban environment.

The two species are both introduced species.  In North America, they are rarely found very far from human-altered landscapes.  I see a fundamental difference in the habitats of these two species.

A couple of decades ago, my wife and I had the pleasure of touring Scotland.  At the northeast tip of Scotland at John O’Groats, we had the pleasure of seeing wild Rock Doves. The birds were nesting on the dramatic cliffs and permitted no close approach by humans.

Obviously, humans befriended some Rock Doves, which readily adapted to urban and agricultural habitats. Don’t expect to see Rock Doves in Baxter State Park or other areas with sparse human population density.

Finding House Sparrows in a city is a snap.  But where you would you go to find House Sparrows in the wild?  A small population of House Sparrows in the Middle East associated with natural grasslands are the only “wild” House Sparrows extant.  This population is genetically distinct from all other House Sparrows.

The vast majority of House Sparrows are associated with humans.  The “natural” habitat of House Sparrows is best described as human-altered landscapes.

With the exception of the Middle East grassland House Sparrows, these birds have married their fortunes together with humans.  The presence of humans has certainly facilitated the natural spread of the species into Europe and Asia.

The original range includes northern Africa and most of Eurasia.  The species has been introduced to North and South America, Australia and New Zealand. Pinning their success to humans, House Sparrows are doing well. They certainly outnumber humans on this planet.

House Sparrows were introduced in North America by releases of birds in Brooklyn in the fall of 1851 and the spring of 1852.  The invasion of North America was aided by subsequent introductions in San Francisco in 1871 and 1872 and in Salt Lake City in 1873 and 1874.  Now House Sparrows are found throughout the Lower 48 states except for southwest Texas and are found over much of Canada.  They have not become established in Alaska yet, likely because the relatively sparse human populations in that state to provide House Sparrow habitat.  Birders in Alaska have found occasional strays including five from northwestern Alaska that may have arrived from Siberia.

An introduced species may wreak havoc on native species. House Sparrows certainly compete with birds that live and nest in our urban, suburban and agricultural habitats.  House Sparrows readily nest in cavities.  Bluebirds, Tree Swallows and House Wrens may lose nest cavities to House Sparrows.

From personal experience, I know that House Sparrows will enter nest boxes occupied by bluebirds and kill the nestlings and then take over the nest box. An effective way to deter House Sparrows is to have the nest box openings no greater than 1.25 inches in diameter.  That opening give access to bluebirds, swallows and wrens but not the chubbier House Sparrows.

The diet of adult House Sparrows is primarily seeds. In agricultural areas, House Sparrows may become pests on cereal grains.  Parents feed their young insects.

In 1958 in China, Mao declared House Sparrows to be one of four pests that needed to be eradicated. The Chinese citizens were told to kill as many House Sparrows as possible.  Perhaps over a billion birds were exterminated.

Rice crops seemed to improve at first but the insects feeding on the crops increased rapidly in the absence of the House Sparrows.  More rice was lost to the insects than to House Sparrows. Mao reversed his position, ordering the protection of the House Sparrow. Rice crop production improved thanks to the dietary needs of nestling House Sparrows.

Sandhill Cranes in Maine; Mallards and Field Guides

By in Field Guides, Species Accounts

In 2000 and 2001, Scott Melvin documented breeding by a pair of Sandhill Cranes at the southern end of Messalonskee Lake in Kennebec Count.  This exciting discovery was the first record of breeding by this species in the state.

Multiple pairs now nest in this area.  In addition, Maine birders have found other Sandhill Cranes in the late spring and summer.  These locations include North Yarmouth, Auburn, Leeds, Chelsea, Manchester, Fryeburg, Smithfield, New Gloucester, Orland, Surry, Unity and Mount Desert Island.  At least some of these cranes may be breeders as well.

The breeding range of Sandhill Cranes spans the western two-thirds of Canada into Alaska with some birds breeding in Minnesota, Wisconsin and Michigan.  Most of these birds winter in west Texas, southern New Mexico and northern Mexico.

The birds migrate in groups with families staying together. The birds fly in the efficient V-formation.  Birds tend to stop at traditional stop-over areas, the Platte River in Nebraska being one of the best known.  In the spring, half a million cranes stop along 70 miles of the Platte River, delighting birders and naturalists.

A resident, non-migratory population occurs in peninsular Florida.  The first Sandhill Crane I ever saw flew above me when I was running a road race in Melbourne, Florida. The size, color and the extended neck (different from the S-shaped, recurved neck of a heron in flight) clinched the identification.

We know that some bird ranges are expanding or changing. Most of these changes we attribute to global climate charge. Fifty years ago, Turkey Vultures, Tufted Titmice, Carolina Wrens, Northern Mockingbirds, Blue-winged Warblers and Northern Cardinals were not a part of Maine’s avifauna.

But how do we explain the arrival of Sandhill Cranes as breeders and migrants in Maine when Maine is south of most of their breeding areas?

We know that the population of Sandhill Cranes in Minnesota, Wisconsin, Michigan and western Ontario is doing well.  The populations there nearly doubled between 1980 and 1995 and continues to grow. Some of these birds seem to be dispersing east. Recent nesting has occurred in northwestern Pennsylvania, southeastern Ontario and Quebec.

We do not know if the recent breeding in Maine represents a true range expansion or a recolonization of a species that was extirpated 200 years or more. We have some evidence from historical accounts from the 1600’s and 1700’s referring to cranes in Maine and Nova Scotia.  However, those authors may have confused cranes with herons.  It does seem clear that some cranes migrated all along the eastern seaboard in the 1600’s before succumbing to human depredation.

If you want to see these magnificent birds, Messalonskee Lake is the place to go.  From I-95, take exit 112 in Augusta and head northwest on Route 27 for about 7 miles.  On the right, there is a parking area where a former motorboat launch was located.  Scan to the south from the floating dock.

Then go 0.2 mile north to Hammonds Lumber. From the parking lot, scan the marsh.  A little patience will usually reveal a crane or two.

Mallards in Maine

Mallards are common birds in Maine.  Even the most casual Maine birder has likely seen this species in our state.  However, you wouldn’t think so based on the maps in several bird field guides.  Jane Coryell has been enjoying Mallards for years on Togus Pond in Augusta.  She happened to notice that the Peterson Field Guide, the Stokes Field Guide and the Sibley Guide to Birds (First Edition) all fail to show that Mallards occur in Maine on the range maps!  Is this error a coincidence or perpetuation of an error by one author in other author’s field guides?  This oversight is yet one more example of why we should be skeptical about what we read.  Paper does not refuse ink.

Bird Nests

By in Reproduction

The nesting season continues apace for many Maine breeding birds.  Finding a bird’s nest can be difficult during the incubation period when the incubating parents are still and rarely leave the nest.  For songbirds and other birds whose young require feeding (altricial birds), the necessity of frequent visits to the nest to satisfy the seemingly insatiable appetites of the nestlings makes it easier to locate nests after the chicks have hatched.

Birds of a given species make similar nests.  Nests range from small depressions in the forest floor or on a sandy beach to massive structures weighing more than a ton.  In today’s column, I will provide an overview of the diversity of bird nests.

The simplest nests are scrapes on the forest floor, fields or beaches.  The nest of a Killdeer is a good local example.  The female lays four eggs in a nest scrape just big enough to contain the eggs.  As you would expect, the eggs are well camouflaged.  In the woods, American Woodcocks and Whip-poor-wills create nest scrapes for their eggs.  For most species that create nest scrapes, little effort is made to line the nests with soft material.

Most birds construct a bowl-shaped nest just large enough to fit an adult’s body.  We can consider the bowl-shaped nest of an American Robin as a typical nest.  Robins are not great architects but still have a remarkably complex nest.  The outer part of the nest is formed of twigs, coarse grass and sometimes pieces of cloth, string or other human-made products.  This outer layer gives the nest strength.  Within this outer layer, robins place a smooth layer of mud.  Finally, a layer of fine grasses is laid down to surround the eggs and aid in insulation.  Once the outer part of the nest is built, the female sits in the middle of the nest for the rest of the construction.  A snug fit is therefore guaranteed for the incubating mother.

Other species use specific materials for the inner lining of their nests.  Palm Warblers, a ground-nesting species in bogs, often place Ruffed Grouse feathers in their nests.  Tree Swallows line their nests with feathers, particularly white ones.  In the early breeding season, you can see aerial fights where Tree Swallows attempt to take white feathers from another Tree Swallow.

Ruby-throated Hummingbirds create tiny nests to hold their two eggs.  The nest is made of down and small pieces of plant material bound together with spider webs.  The outer part of the bowl is covered with bits of lichens to aid camouflage.

Black-capped Chickadees make their nests in a tree cavity.  The outer part of the nest is made of moss and the inner part of spider webs, soft grasses and plant down.

Waterbirds typically create bowl-shaped nests on the margins of lakes or ponds or even on floating vegetation.  In most cases, the outer layer of the nest is made primarily of vegetation.  If water levels rise, waterbirds will quickly add additional vegetation to keep the inner part of the nest dry.  The inner lining is made in part of down feathers that the female pulls from her breast.  These down feathers create a wonderfully warm place for the eggs.

The largest nests in Maine are made by birds of prey.  An Osprey nest may be five feet across.  The outer portion is made of sticks and miscellaneous debris.  The inner lining is made of smaller twigs, grasses and other soft material.

Bald Eagle nests are larger yet.  Some nests may be eight feet in diameter and 12 feet high, weighting over a ton!  Like Ospreys, Bald Eagles use the same nests year after year, adding material to the nest each spring.

A good source for identifying nests based on their structure and location is http://nestwatch.org/learn/how-to-nestwatch/identifying-nests-and-eggs/

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