Saturday, December 28, 2013

This Week's Crops & Clips: Northern Harrier

We recently visited Green Cay Wetlands in Boynton Beach, Palm Beach County, Florida. This is the nature center and the beginning of one loop of the well-maintained boardwalk.

Green Cay Nature Center 4-20121226

 As we walked a mile and a half along the boardwalk, a Northern Harrier made several passes over the area, but I failed to get very good images.

 Northern Harrier 6-20131210

Northern Harrier 8-20131210

Then, just before we departed, it flew right towards us, into the wind. 

Northern Harrier 7-20131210

Northern Harrier 20131210

The harrier performed a series of low-level stalling maneuvers-- gliding upward and then suddenly falling almost to the ground before it regained lift. 

Northern Harrier 3-20131210

Northern Harrier 5-20131210

Since the harrier glides with its wings configured in a strong dihedral angle (V-shape), it can safely regain lift at slow speeds because only one wing stalls at a time. The high dihedral angle increases the rolling motion of the bird, so the opposite wing quickly regains lift, restoring stability. Turkey Vultures, Golden Eagles, and many seabirds also position their wings in this manner as it permits much greater stability in slow low-level flight.  The alternating stall and recovery of each wing causes the vulture's wings to tilt back and forth while it sails.

Northern Harrier 4-20131210

Northern Harrier 2-20131210

Saturday, December 21, 2013

When birding gets slow...

For the past few weeks it has been relatively quiet on our local south Florida birding patch. Numbers and varieties of birds have decreased for several reasons. 

The rainy season extended into November, maintaining high water levels in the wetlands. This disperses prey species. Sight feeders such as herons and egrets are not concentrated in the canals. Mudflats are not yet exposed to attract sandpipers. Tactile feeders, including Wood Storks and ibises cannot forage effectively in water that is deeper than the length of their bills. 

This time of year, mud flats should be exposed along the edge of the lake. The prolonged high water levels have encouraged the accumulation of periphyton, an essential element of the food chain in the Everglades ecosystem. A complex mix of "algae, cyanobacteria, invertebrates. secretions, and detritus attached to submerged surfaces," periphyton serves as a food source for fish and invertebrates. It improves water quality by adding oxygen and recycling nutrients and nitrogen from agricultural pollutants. Read more about periphyton here.

Note the mat of periphyton floating on the surface.

Periphyton floating at edge of lake 20131215

The arrival of the Yellow-rumped Warblers signaled the end of warbler migration.  

Yellow-rumped Warbler 20131209

Sparrows, goldfinches, waxwings and flocks of robins have not yet appeared, with a few exceptions. While they overwinter in our area, their local abundance varies greatly. 

Earlier this fall, we had  brief visits by three sparrow species, but none chose to linger more than a day or two. 

I sighted a Lincoln's Sparrow only once, on October 16.

Lincoln's Sparrow 20131016

Ten days later, two White-crowned Sparrows showed up and lingered for a week.

White-crowned Sparrow 2-20131026

Another one-day wonder was this Swamp Sparrow, on December 4. 

Swamp Sparrow PICASA 2-20131204

A single American Robin appeared on December 5. This is odd, as they usually arrive in large flocks more towards the middle of winter.

American Robin 20131205

Disturbance of the land has increased. As related earlier, we lost our "Fake Hammock" with its five mature Florida Trema trees due to vandalism and fire caused by the gang of off-road vehicle riders. In addition, a new roadway is being pushed through adjacent to the Yellow-crowned Night-Heron rookery.

The rookery occupies the trees on the opposite side of this canal-- a peaceful enough scene, looking south, ...

Heron rookery south end 20131208

...but the view from the same spot, looking north, reveals the construction.

Heron rookery construction north end 20131208

The noise and human activitiy caused by excavation and grading, milling and paving is having its toll on the rookery. Although the herons will not be courting and building their nests until late March, I often find a few roosting there all year 'round. Since construction started, I have twice seen one Black-crowned Night-Heron at the location, but only once this lone Yellow-crowned Night-Heron. It appears to be retching, perhaps attempting to disgorge some undigestible prey remains, but nothing ever came out of its mouth..

Yellow-crowned Night-Heron retching 20131208

I stopped visiting the rookery area except for weekends, when the workers and machinery are inactive. 

Construction next to heron rookery 20131117

A pair of crow-sized Pileated Woodpeckers still occupy the remnant of woodland that has not been killed by herbicides in preparation for the roadway extension.

The male sports a red "mustache."

Pileated Woodpecker male 20131208

He drummed atop a wooden utility pole, attracting the female.

Pileated Woodpecker pair 2-20131208

They provided me with some of my few flight shots of Pileated Woodpeckers.

Pileated Woodpecker in flight 3-20131208

Pileated Woodpecker in flight 2-20131208

On these quiet days I tend to stay in one place, with the rising sun behind me, and allow the wildlife to reach a baseline state of equilibrium. A favorite spot is next to one of the few remaining fruiting Trema trees. On one occasion the loud and brief shriek of a Blue Jay broke the silence as other birds dove for cover. The cause of their distress was evident a second later as an immature Sharp-shinned Hawk flew in rapidly and perched right in front of me.

Sharp-shinned Hawk 20131123 

A few days later, in the same tree, a Northern Flicker provided me with a very nice photo opportunity.

Northern Flicker male 20131217

A Gray Catbird perched nearby.

Gray Catbird 3-20131217

In an adjacent exotic Brazilian Pepper tree, a Blue-gray Gnatcatcher eyed me.

Blue-gray Gnatcatcher 2-20131206

An immature Red-shouldered Hawk rested on the dried-out flower of a Royal Palm.

Red-shouldered Hawk 20131208

From an upper branch, a male Boat-tailed Grackle's iridescent coat reflected all the colors of the rainbow.

Boat-tailed Grackle 20131208

Just as the birding slowed down, the butterflies increased.

I found two butterfly species that were new to my patch, the Common Buckeye...

Common Buckeye 2-20131203

... and a Silver-banded Hairstreak.

Silverbanded Hairstreak - Chlorostrymon simaethis 20131203

Monarch butterflies are declining in number due to loss of habitat containing milkweed, host for their larvae. Their winter home in Mexico is also being destroyed. I could not resist this shot of one against the sky.

Monarch butterfly on Lantana 20131208

Sunday, December 15, 2013

The helpful monotony of patch birding

Birding is an exercise in statistics. Finding a certain bird depends upon the probability that the birder's path will intersect with that of the bird at a given moment in time. For more common birds, this probability is high because we are not looking for a single bird, but rather one that represents the species. A knowledge of birds' habits and habitats greatly increases the chance of a successful quest; the bank robber selects banks because "that's where the money is."

Very few other birders visit our favorite birding patch, mostly because it is only accessible via private or posted land. Trails in the patch itself are open but there are restrictions against use of motorized vehicles, overnight camping and open fires. There are no Internet bulletins alerting us to unusual finds.  Although we have seen some birds that are uncommon, we have reported only one or two truly unusual species from this location.

Harbour Lakes wetlands 20131203

We walk the same old local patch, morning after morning. Often we are there before the sun rises and may walk and watch for two or more hours. We see the same old resident birds, and the same old migrants visit or stay for the winter. Our expectations are not high. If we set out to see a specific less common species, more than likely we will fail in our quest.

Yet we are open to discovery. We notice the incremental changes-- the rise and ebb of water levels in the wetlands, the flowering and the fruiting, destruction and sometimes restoration. We have grown accustomed to all the snags and rocks and shadows that look like distant birds and mammals, and we notice the new garbage bag or the out-of-place shadow that may be a fox, or a Bobcat. We are always alert for non-avian subjects.

During the past seven years of walking this patch nearly every morning we have found 135 species of birds, recorded since 2009 in our eBird List of Species, West Miramar Water Conservation Area. Most of these we documented among over 5700 photographs on FLICKR for this site alone. 

Interestingly, some of these we have seen only once or twice. Despite our regular observations of this area, we have been there only a tiny fraction of all the daylight (and none of the nighttime) hours over the past nine years since first setting foot there. Statistically, our records are insignificant. How many birds have we missed just by minutes or days or years?

On a still morning the slight rustling in a shrub, easy to overlook, revealed the first Orange-crowned Warbler we ever saw in the patch, though once we learned where to look for them we have seen several more.

Orange-crowned Warbler 20101231

The stirring of a single blade of grass invited us to find our first Rough Green Snake, wet from the morning dew. It responded to my approach by retreating across a sandy patch and rearing up towards me like a tiny cobra.

Rough Green Snake 2-20091025

A flash of yellow color in the brush disappeared as suddenly as it appeared, and a lucky photo documented our first and only Yellow-breased Chat. Uncommon but not rare, our patch must have been visited by many more chats besides this one so fortuitously sighted.

Yellow-breasted Chat 20101231

A shy and retiring Black-whiskered Vireo showed itself during only one of our hundreds of visits to this particular thicket. How many times had it been there when I was otherwise occupied?

Black-whiskered Vireo 3-20110420

A dull-plumaged Bell's Vireo presented an identification challenge. We have seen it only twice, in October of 2009 and 2012.

Bell's Vireo 5-20091023

Short-tailed Hawks flew over only twice. This is the more common dark morph, seen this past October. I wonder how many I missed by not scrutinizing the vulture flocks which help disguise them from their usual prey of small birds.

Short-tailed Hawk dark morph 20131023

This dissimilar light morph was the first Short-tailed Hawk on my life list of species first seen (and photographed).

Short-tailed Hawk SOOC Cropped 4-20100108

A few more spectacular birds have shown up on only one occasion. They include a small flock of Roseate Spoonbills that appeared in late November, 2012 and stayed for three weeks.

Roseate Spoonbill 3-20121205

Roseate Spoonbill 4-20121125

Remarkably, the spoonbills were joined by our first and only flock of White Pelicans, a species that also lingered for several days. Neither species has reappeared since.

Pelicans with spoonbill 2-20121125

Reddish Egrets are rarely seen away from the coastal brackish waters, yet a single immature bird visited us,18 miles inland, and lingered for over a month. As is typical, it pranced about erratically in search of prey.

Reddish Egret dance 4-20110408

Reddish Egret immature 20110426

The highlights among rare visitors were two Whooping Cranes, the first ever reported this far south in Florida. They were captive-reared in Wisconsin and released to migrate on their own. One injured its foot and had to be treated and rehabilitated and was released in Tennessee. The other lacked survival skills and was relocated to a ranch in central Florida. Sadly, both perished during the winter.

Whooping Crane 12-15 at 0850AM  20130207

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Thursday, December 12, 2013

This week's Crops & Clips: Blue Jay

After I captured these views of a Blue Jay busily foraging for acorns, I realized that I have far too few photos of this common yet beautiful bird. I caught this one in a baseline state.

Blue Jay 20131117

Blue Jay 3-20131117

Several acorns can be stuffed into one gular pouch.

Blue Jay with acorn 20121021

Blue Jay with acorns 20110105

Jays take up the highest perches, watching for intruders, ready to sound the alert.

Blue Jay 20101210

Blue Jay 20120128

Blue Jays are so common that I don't feel an urge to photograph them, and when I do they seem to be smart and wary. Like the Steller's Jays in New Mexico, their shadows often fall on mine as they follow me with the sun at their backs.

Blue Jay 20110425

They like to keep some vegetation between them and the camera.

Blue Jay 2-20130719

Always on guard, Blue Jays are easily agitated, whether simply by my presence or because of some real or imagined threat. The excited call of one summons hordes that appear out of nowhere.

Blue Jay near Eagle nest 20091216

Blue Jay Calling 20081020

Bellicose and unafraid, they mob or attack owls eagles, large hawks, some falcons as well as cats and anything smaller and weaker.

I watched three jays chase a Merlin that could have killed any one of them. This American Kestrel was fair game.

Blue Jay and Kestrel 20101210

Blue Jay and Kestrel 2-20101210

The kestrel retreats, but the chase is still not over.

Blue Jay and Kestrel 4-20101210

Loggerhead Shrikes may eat small birds, but they are no match for this scruffy jay in molt, who retained his perch as King of the Roost

 Shrike and Blue Jay 20110730

I obtained a rare intimate portrait.

Blue Jay portrait 20121021