Do Birds Retire?

Red-shouldered Hawk

Red-shouldered Hawk, Buteo lineatus

 

As I approach that golden age of retirement my birding hobby causes me to look to the avian world for guidance.  Do birds retire and perhaps seek that perfect habitat where food and water are plentiful and the temperature ideal all year long?  Do they give up those long migrations and the work of nesting and breeding?  Do they recreate with other aging birds, have more time for song, or perhaps help with raising of the grand and great-grand chicks?  Birds, I know do not crave a large nest egg; for them that just signifies the nefarious work of a parasitic cowbird and means another large mouth to feed.  (See earlier post “Birds Behaving Badly / Brood Parasites”, 8/22/2015)  In short, is there a golden age for birds?

Ruby-crowned Kinglet

Ruby-crowned Kinglet, Regulus calendula (click on any photo to zoom)

There seems to be two distinct approaches to this issue in humans; those who want to keep working or must work until they die in the saddle, and those who crave and can afford the free-time of retirement.  You can’t explore these issues for birds until you figure out how to determine the bird’s age, and they don’t make that easy.

Indigo Bunting

Indigo Bunting, Passerine cyanea

Bird size is not a reliable dating tool, nor is bird song.  Some have observed that second year males often have weird or incomplete versions of the adult song, but you can’t rely on it for dating.  Early dating by plumage is straight forward, using natal down and the rapid progression to juvenile plumage, which is usually duller than the adult’s and often spotted or striped.  But by late summer, fall, or early winter, depending on the species, the “first winter” plumage develops which is usually very similar to the adult.

White-eyed Vireo

White-eyed Vireo, Vireo griseus

Judging the age of adult birds then becomes much more difficult.  The annual or biannual molt makes the shabby and worn out feathers all new again, like repairing the wrinkles of age.  Wouldn’t a yearly face-lift or tummy tuck be great?  Luckily some birds, gulls in particular, have a yearly progression of plumages allowing first year, second, third, and adult age designations.  Learning these variations is difficult and requires a good guidebook or an experienced colleague.

Brown Pelicans

Brown Pelicans, Pelicans occidentals (adult above and juvenile below)

Another dating technique is called skulling.  One can observe the air cavities in the bird’s skull by wetting and separating the feathers.  The maturing skull apparently goes through a specific and progressive pattern of pneumatization and maturation, visible through the bird’s thin skin.  This is obviously a tool for ornithologists–don’t try this at home.  That leaves banding, the most definitive technique in determining the birds age, but again a technique for the experts.  These basic facts are now known:  birds in the cooler temperate zones live shorter lives than those in the tropics, rural birds live longer than urban birds, large birds live longer than small birds, and young, inexperienced juveniles have the highest mortality rate of all.

Mottled Duck & Ducklings

Mottled Duck & Ducklings, Anas fulvigula

I was surprised to learn that the annual mortality of passerines was 70% in the temperate zones.  The longevity record for the Bald Eagle and Osprey is 22 years, 16 years for a Northern Cardinal, and 7 years for a House Wren.  But these were the lucky ones.  Message to birds:  avoid risky juvenile capers, leave the city and head to the tropics and stay there, and don’t volunteer to be a canary in a coal mine or a clay pigeon.

House Wren

House Wren, Troglodytes aeon

D.J. Holmes and others, writing in “Experimental Gerontology”, has noted that birds have relatively longer life spans compared to similar sized mammals, especially given their warm body temperatures, rapid heart rates, high glucose levels, and high metabolic rates.  These are usually harbingers of rapid aging, but not so with birds.  Some seabirds in particular age very slowly and actually increase their reproductive activity with age.  Apparently birds have evolved specific adaptations to offset the cell damage caused by oxidative and glycosylative compounds, mechanisms not found in mammals.  Is there a hidden “Fountain of Youth” under all those feathers?

Dark-eyed Junco, AKA Snowbird

Dark-eyed Junco, Slate-colored, Junco hyemalis (AKA Snowbird)

So it turns out that birds do not retire and enter a life of leisure but rather press on or even increase their activity and fecundity with age.  That is until they just drop, fly into a window, or are snatched away by a more agile hawk or owl.  I’m sorry to learn this, but maybe we humans can adapt some of their techniques for staying young.  Life in the tropics sounds good, so I for one will become a “snow bird” and head south this winter.  I’m also interested in those avian chemical adaptations.  Maybe there’s an investment opportunity lurking here.

The Least Birds

IMG_6546

“Least” is the superlative on the short end of the scale.  It’s a modifier that may be complimentary or derogatory but in the birding world it just describes size.  I was noticing some terns roosting on the dock pilings this week.  The Royal was large and obvious, while the smallest were more vocal and active, hovering and diving while the others just watched.  These were Least Terns and brought to mind the other common “least” birds, the sandpiper, bittern, and flycatcher.

For me the Least Terns were the easiest terns to learn and ID, mainly due to their size and an obvious marking.  The ID’s become much muddier for the next size up when you have to deal with the Common, Forster’s, and Roseate Terns with their subtle differences.  In addition to being our smallest tern, that white chevron on the forehead of breeding adults is unique.  The Little Tern is a similar-appearing East Coast vagrant from Europe, but other than that potential confusion, the Least Tern is usually an easy ID.

Least Tern, Sterna antillarum

Least Tern, Sterna antillarum

This little bird has been losing it’s competition with bathers, beachcombers and condos for nesting sites on the beach, but now you do find some roped-off dunes.  The bird’s innovative and resourceful impulse has led it to “protected” nesting on the gravel roofs of shopping plaza, including our local Acme.  I guess there is some benefit to all these big box stores.  Thankfully the milinery hunters of the 19th century are no longer a threat.  Say goodbye to this bird in late summer as it completely leaves the mainland U.S. and northern Mexico for unknown wintering grounds further south.

Least Sandpiper, Calidris minutilla

Least Sandpiper, Calidris minutilla

The Least Sandpiper also comes in as the perceptible light-weight of the peeps.  The guidebooks only list it as 1/4 to 1/2 inch smaller than the Western and Semipalmated Sandpipers but the size difference is noticeable when you see them in a group.  Often however, this bird congregates in small feeding flocks away from other larger shorebirds in sheltered coves and along marsh edges. It’s the most common sandpiper to be seen on small inland lakes.  I find that the pale yellow legs is the most helpful field mark–the other peeps have black legs.  I know the caution about muddy legs obscuring the yellow, but you usually can find one bird in the flock who likes to keep her legs clean.

IMG_7012

Least SP; also notice slightly drooping bill tip and more brown than other peeps

The birds breed in Canada and Alaska but appear along each coast and the Great Lakes in mid-June, hanging around through September.  I find them in Florida and the deep south all winter.  I’ve learned from experience and fellow photographers that you really need to get low on the beach, kneeling or lying prone to get good shots of the shorebirds.  I usually just kneel.

For the other two “least” birds the modifier is valid for not just their size.  The Least Flycatcher and Least Bittern are among the least often seen, least photographed, and least properly ID’ed birds, at least for me.  Forgive me for showing photos of related birds only–I’ll keep stalking the others for decent shots.

Great-crested Flycatcher, Myiarchus crinitus

Great-crested Flycatcher, Myiarchus crinitus

The Least Flycatcher is common here but easily confused with the other 4 members of the genus Empidonax that are also seen in the Eastern U.S.  They all have wing bars and eye-rings and their size differences are only measured in 1/4’s of inches.  This is where “advanced birding” techniques apply.  The best differentiaters are their songs and habitat preferences, but you’re often left with just calling them all “Empids”.  The Least FC prefers the partly open edges along woods and has a loud “che-beck, che-beck…” song.

Green Heron

Green Heron, Butorides virescens

I saw the elusive Least Bittern at a distance in the STA5 water control area in south/central Florida in 2012 with a large group of experienced birders.  Despite its relative abundance the wonderful camouflage and secretive feeding habits make it one of the more difficult sightings.  I think it’s closest look-alike is the Green Heron rather than the larger American Bittern.  I’ll show you photos of both–it’s the least I can do.

American Bittern

American Bittern, Botaurus lentiginosus