Impressive numbers at Boca de Pacora

The news spread through the social media... a vagrant (for Panama) Large-billed Tern appeared in the coast of the upper Bay of Panama close to the mouth of the Pacora river (Boca de Pacora) to the east of Panama City... and we were after him! Under the guidance of Karl and Rosabel Kaufmann, Stephany Carty, Rolando Jordan and your blogger host rode the intricate dirt roads through pasture lands, scrubs and patches of gallery forests in order to reach the beach.  The one-hour drive resulted in some nice birds of course, like this obliging and aptly-named Roadside Hawk.

Roadside Hawk

I took the above photo from the car... in fact, we only left the cars in order to watch a roosting Barn Owl (always nice to see an owl in daylight) and to find a calling Striped Cuckoo that turned out to be a life bird for Rolando!

Striped Cuckoo

Eventually, we reached the beach.  The surf was quite away, but the tide was raising.  The extensive mudflats were full of waders and other water birds.

Boca de Pacora beach

We checked first a sand bank where Rosabel's group saw a family of American Oystercatchers with a recently fledged young some days ago.  There are few breeding reports of this species in the upper Bay of Panama, including mine some years ago while celebrating with my wife our anniversary (check this post).  We saw at least 12 different oystercatchers at the site that day, some of them doing courtship displays.

American Oystercatchers

As the tide was rising, the birds began to gather closer to the coast.  Impressive flocks of Neotropic Cormorants, Brown Pelicans and Magnificent Frigatebirds obscured the horizon... but more important, flocks of migrants also started to appear.  It is the middle of June and these species shouldn't be in Panama... at least not in such numbers: tons of Sandwich, Gull-billed and Common Terns were quite unusual... and no less than eight Caspian Terns also add some color to the flock.

Caspian Terns

The most common species was the Black Skimmer.  Close to one hundred birds were resting at the beach.  However, these birds probably belongs to the South American subspecies cinerascens, which are larger than the North American birds, with gray wing linings and tails and thin white trailing edge to the wings.

Black Skimmers

Black Skimmers

Although we found most of the previously reported species for the area, the Large-billed Tern did not appear again.  We had to leave the place since a huge rainstorm was about to hit us, but we were happy anyway knowing that all those birds still call Panama their home!

Dark clouds over Boca de Pacora

At the mouth of the Pacora river

The upper Bay of Panama comprises 48,919 ha of sandy beaches, mudflats and mangrove forests along our central Pacific coast.  The western end of this area is under great pressure by urbanization and the expansion of Panama City and, until recently, its protected status was threatened by particular and economic interests.  Iconic sites (for shorebirds watching) included in the Upper Bay are Panama Viejo, Costa del Este and Juan Díaz (although the first two are out of the protected area); however, I just visited a new site at the mouth of the Pacora river where the Panama Audubon Society (PAS) has conducted shorebirds surveys since some years now in association with others NGOs, like the National Audubon Society and the Center for Conservation Biology, among others.

That's me in Panama Viejo.  Notice the peeps in the background (photo by Osvaldo Quintero)

Getting there ain't easy... the muddy road from the Panamerican highway is slippery and rough in some sites... and it is at least a 1-hour long drive to the beach.  However, this road crosses open habitats, shrubs, gallery forests, rice fields and some wetlands that are highly diverse in terms of avian species.  We did several stops along the way to watch some interesting species... I was driving, so I did'n take so many photos in this part of the trip.  Once in the beach, we started to work..., yes, to work.  This was not an usual birding trip.  With us was a grad student in Marine Biology of the Universidad Internacional Marítima de Panamá, Stephany Carty, some volunteers, an academic advisor from the Universidad de Panama and PAS' resident biologist, Michele Caballero.

Stephany and a volunteer sampling at the study site

Stephany is doing her thesis in these mudflats, characterizing benthic organisms associated with resting and feeding areas for resident and migratory shorebirds (benthic refers to the collection of organisms living on or in sea or lakes bottom -thanks Michele for the explanation).  This and other studies have the aim to begin a process of documentation of this critical habitat with hemispheric importance for shorebirds, and the PAS is supporting these studies while at the same time makes an important work of environmental education in communities adjacent to the protected area.

Western and Least Sandpipers at the beach

In the other hand, PAS' Executive Director, Rosabel Miró, and others PAS members (including me) were searching banded shorebirds.  Last season, some sandpipers were fitted with coded leg flags allowing individual identification.  Those flags assigned for Panama were gray with black characters (as you can see in the "Pluma Fina" section of this PAS' bulletin).  We saw some huge flocks of peeps, including Semipalmated, Western and Least Sandpipers as you can see in the picture above.  We scoped them, but none of these were banded.  We also saw Black-necked Stilts, Marbled Godwits, Willets, Whimbrels, Short-billed Dowitchers and my favorite shorebird: Red Knots.

Black Skimmers, Short-billed Dowitchers and Red Knots

These birds were easily identified by their pale red underparts, reminiscent of their alternate plumages.  This is an uncommon species in Panama and it seems to have declined in the last years.  In fact, this species is object of intense research because the populations wintering in South America dropped over 50% from the mid-1980s to 2003 (article in pdf here).  Not only waders, we also saw hundreds of other species, like resident Brown Pelicans and Neotropic Cormorants plus an amazing number of terns species... the most common were the Elegant Terns, but at the end we recorded six different terns species, including some uncommon Caspian Terns.

Caspian Terns

Notice the red, heavy-looking bill and the dark underside of the outer primaries in flight.  The highlight were three Common Terns seen flying first and then resting in the sand.  They are not common at all in Panama, as its name may suggest.

Common Terns, Willets and Semipalmated Plovers

In the picture above you can see the Common Terns resting close to a flock of Willets and two Semipalmated Plovers (we saw five plovers species in total).  The slender profile and black carpal bar is characteristic.  However, the most abundant (and intriguing) tern-like species was the Black Skimmer.  A huge flock of these elegant birds were resting in the beach (as you can see in the picture above with Red Knots).  But I noticed something strange when they took off... watch these photos:

Black Skimmers

Black Skimmers

Notice the gray underside of the wings (this can depend on light and angle, but compare the color with the white underparts), the thin (rather than broad) white trailing edge to the secondaries and, more important, the gray tail (instead of white).  All these marks are characteristics of the cinerascens subspecies from South America.

Black Skimmers and Marbled Godwits

The relative abundance of this subspecies with respect to the North American migrants is unknown.  Now I wonder if I have ever seen the North American subspecies niger in Panama (during my first years of birdwatching I didn't notice those details).  As you can see, you can have fun while contributing to scientific knowledge!