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Saturday, April 19, 2014

This week's Crops & Clips: Least Tern

One bird that can be counted on to arrive at our neighborhood lakes by the middle of April is the Least Tern (Sternula antillarum). While it is the smallest of the tern family at about 9 inches long with a wingspan of 20 inches,  it makes up for its small size with graceful energetic flight, strident calls and interesting behaviors.

Four Least Terns arrived on our lake on April 5th, apparently three males and one female. One of the males was in the early courtship stage, posturing before the female and bringing her fish, which she at first refused. 

The pair engaged in recognition displays. I expected that soon they would be in full courtship mode, with the male offering gifts of small fish. 

Least Terns display 20140406


Least Terns display 2-20140406


The male and female plumage is very similar. During breeding season, the larger males are said to have brighter orange-yellow bills, legs and feet, though this is not always noticeable. Note that the male, on the left, is a bit larger and has a brighter yellow bill than the female.

Least Terns 8-20140406


Least Terns 7-20140406


This video, "A Tern is Spurned," documents his failure as a suitor. It is best viewed full-screen (If the video fails to load, visit this link.)





Most mornings I watched the terns' behavior from the shade of this little tree at the end of a peninsula, very near the rocks where they like to roost.


Harbour Lake tern watching spot 20140416


Although it was impossible to identify the individual males, the bonded couple appeared to stay together and they chased off the other males if they tried to roost with them. 


Least Terns interloper 02-20140411


The calm was disturbed when one of the unpaired males flew in and began a bill-up display. The established male blocked the interloper and then chased him away. 


Least Terns 3-20140405


The unwelcome third tern kept an eye on the pair from a nearby rock.


Least Tern interloper 20140407



First one, and then the other male disappeared, and on April 15th and 16th, only one male and female remained. Presumably, the male was the "Spurned Tern." Having failed in his attempts at ceremonial courtship, the male tried a new tack-- he would impress his prospective mate with his fishing prowess. The couple was already on the lake when I arrived before sunrise on April 16th. In the semi-darkness I photographed the male hovering and diving for fish. (Taken at f/5.6 1/640 sec at ISO 1000). 


Least Tern hovering 2-20140416 Least Tern hovering 20140416 Least Tern diving 20140416


  He succeeded and brought home an actively wiggling minnow. 


Least Tern feeding sequence 01-20140416


Dispensing with the feeding ritual, he simply dropped the struggling fish, missed the the female's waiting jaws and quickly flew off, not noticing that she failed to acquire a proper hold. 


Least Tern feeding sequence 02-20140416 Least Tern feeding sequence 03-20140416 Least Tern feeding sequence 04-20140416 Least Tern feeding sequence 05-20140416


The minnow slipped out of her bill and she tried to retrieve it, but the little fish escaped back into the water.


Least Tern feeding sequence 06-20140416 Least Tern feeding sequence 07-20140416 Least Tern feeding sequence 08-20140416 Least Tern feeding sequence 09-20140416 Least Tern feeding sequence 99-20140416


There are three distinct populations (subspecies) of Least Terns in the US. One group nests in limited areas on the beaches of western Mexico and California. A second finds sandy places to nest along rivers and streams in the mid-west. Both of these populations are of particular conservation concern. With protection of its nesting areas, the endangered California population has increased from less than 600 pairs in 1974 to over 4500 pairs, while the interior subspecies have increased to 7,000 pairs from a low of 1,000 pairs in 1985 . 


Our Florida birds belong to the third subspecies, which breeds up and down the entire US Atlantic coast, wintering in the Caribbean and along the east coast of Central and northern South America. All three populations face threats from human activities, notably destruction of beaches and loss of beach and stream-side habitat. Plume hunters took a huge toll in the late 1800s-- I have seen photos of ladies' dainty hats adorned with the whole bodies of one or more Least Terns.  Though not on the Endangered Species list, the U.S. Fish and Wildlife Service lists the east coast Least Terns as a Species of Management Concern. Their swift erratic flight makes it difficult to photograph a Least Tern in flight.


Least Tern in flight 20140416 Least Tern in flight 2-20140416 Least Tern in-flight 4-20110415



Once bonded, the pair stays loyal to each other for the entire breeding season. The male must prove his prowess as a provider by catching fish and offering it to his intended mate. 


Following the age-old Least Tern courtship ritual, the female waits patiently while her suitor hunts for a small fish. When he catches one, he calls excitedly and flies toward the female's position, sometimes adding a dramatic flourish by swooping past her. The female eagerly awaits his arrival, calling back and begging. I captured the courtship ritual during the spring of 2013 in this video, best if viewed full-screen . (If the video fails to display, click on this link).




video



I am quite sure that Least Terns have nested on the gravel roofs of an elementary school and a strip mall in our neighborhood. Young terns are precocious and are able to walk about soon after hatching, but they remain dependent upon their parents until they move south in late summer.


In late summer, 2012 I watched these two immature terns as they were being trained to fish by their parents. The adults would catch a fish and make their youngsters chase after them. The adults would then drop the fish in the water and fly down as if to get to it before the "trainees." If not retrieved, the parents would pick up the fish and try all over again.  Note that the white area on the forehead of the adult, to the left in this photo, is enlarging. After breeding the adults' bills and feet also become darker.


Least Tern adult w 2 juveniles 2-20110727 



Least Tern immature in flight, July 27, 2011.


Least Tern immature in flight 4-20110727 




First-year birds may remain on their wintering grounds through the next breeding season.

Saturday, April 12, 2014

This week's Crops & Clips: Northern Cardinal

It is impossible to pass by a cardinal without taking a second look, or a photo (usually many) if camera is in hand. As a child I remember my grandmother called it a "Redbird," and that name stuck until I got my first bird book. I didn't know it, but way back then the New York City area was only beginning to celebrate the return of this species. During the first quarter of the 20th Century it had inexplicably withdrawn from the northern limits of its range. 

Northern Cardinal 20110330

Ludlow Griscom wrote, in 1923 (Birds of the New York City Region, Amer. Mus. Nat. Hist., NY), that the "Eastern Cardinal" had been "extirpated" from the area. Its return to my home turf in New Jersey during the 1930s and 40s was variously attributed to milder winters and the increasing number of bird feeding stations. 

Female Northern Cardinal 20091228

I was gifted with a copy of Allan Cruickshank's 1942 edition of Birds Around New York City, which became my point of reference when I found an unusual bird or one during an unexpected time of year. Cruickshank described the cardinal as "...slowly but steadily re-establishing itself northward... Like all permanent residents which reach the northern limits of its range here, the Cardinal is subject to severe winter killings." 

Northern Cardinal close 20111104

Later, John Bull would write: "The increase and spread of the Cardinal in the New York City region, as well as throughout most of the northeast, particularly since the mid-1940s, and more especially in the 1950s, has been positively phenomenal. Few, if any, species have made such gains" (Birds of the New York Area, 1962). Since that time we have seen extraordinary range expansions of other bird species, for example the House Finch, Cattle Egret, Boat-tailed Grackle, White-winged Dove, Eurasian Collard-Dove and the steady northward shift of the breeding grounds of many native land birds.

Northern Cardinal female portrait 20131031

In the above portraits I have provided equal space for both male and female Northern Cardinals, for if one captivates us with color, the other subdues us with softness.

Northern Cardinal 2-20121226


Female Northern Cardinal 20090225

Cardinals may be North America's most welcome visitors to water features and back yard feeders.

 Northern Cardinal 20131102

Northern Cardinal female 2-20131102

Northern Cardinal 20130218

Northern Cardinal 20130310

Because I took up photography after moving to the sunny South, I suffer a notable absence of images of red cardinals on white snow, a magnificent combination. However, if you look closely at this coy female peering around our daughter's feeder in Illinois, you may catch a few snowflakes.

Northern Cardinal 20130305

In the interest of fairness, I should also embarrass this adolescent male before he has time to dress in his finery. Note the dark bill which will become fully red as an adult. 

Northern Cardinal 2-20120808

An adult male in molt can be a sorry sight. I can't blame him for hiding behind a leaf!


Motley Cardinal 20100826