Osa Birder


Tricky Identifications

Liz Jones

Liz and husband Abraham Gallo own and operate Bosque del Rio Tigre, a lodge in Dos Brazos that specializes in birding.  You may reach her at liz@osaadventures.com


Lots of the birds are easy to ID and there can be no doubt as to which species you are observing, but many present difficulties that take a bit of practice and experience to overcome.

One should never jump to the conclusion that you are seeing a rare bird, or a species out of the normal range, just because the specimen in the field  is not exactly like the one in your field guide.  Birds look different when their feathers are old, while molting, wet, or young.  Some species have different colorations across their ranges, different bill size or de-curvature, even different voices.

1 Yellow-bellied Elaenia

Dusky-capped Flycatcher

Yellow-bellied Elaenia

Using several different references with illustrations by different artists can help a lot. We have many references we use regularly.    But of course no one has all these volumes in the field.

When a birder goes back to home base and starts looking at other books, another problem appears.  One’s memory about what they really saw and what they are seeing in the books can get fuzzy quickly.  It happens to the best of us.

There is a way to get around this problem and best done prior to opening a field guide. The age old practice of taking field notes and/or executing a drawing is a great exercise that will also help develop good ID skills. Of course now that we all have smart phones, we can take a picture, which helps with ID but does not help much with ID skills in the field.

With practice one will learn to check certain field marks.  Often field guides have great introductions with names of all the feathers and body parts as well as notes on ID skills.  My favorite is David Sibley’s intro in The Sibley Guide to Birds.

Pay attention to the color and pattern around the eyes, face, crown, throat, nape, breast, belly and vent. Coloration of the “leg,”which is actually the foot, can be important.  Does the bird have wing bars or margins?  Length, shape and coloration of both the ventral and dorsal sides of the tailshould be noted. Is the bill flat, hooked, or de-curved?  Is there a different coloration at the base of the bill or between the upper and lower part?

Size is also important but also can vary from bird to bird.  I see this variation a lot in the Cocoa Woodcreeper.  It is a good idea to view the bird without binoculars to get a sense of scale.  Also note the size of the bill, wings, tail and head in proportion to the rest of the body.  Sometimes the length of the wing’s primary feathers—its longest ones—will  will determine what specie it is.

Vocalizations are another very helpful tool.  Now, with cell phones, you can record the song or call and compare it to the many examples on line.  Habits, habitat, flight patterns are all important clues.

Range maps can be useful but cannot be counted on completely.  For example, in the first publication of the Garrigues/Dean The Birds of Costa Rica  there were 14 species missing on the Osa maps that had been resident here for many years prior to publication.  There are also birds shown to be on the Osa that as far as we know, have never been seen here.  Two examples that come to mind are the Ruddy Woodcreeper and the Speckled Mourner, the latter nearly impossible to find anywhere in Costa Rica.

Some of the trickiest birds to ID are raptors, gulls, shorebirds, flycatchers and hummingbirds.

Identification of gulls and shorebirds is not a skill easily acquired and requires many hours on the mudflats and shorelines.  Large gulls can go through up to 8 different plumage stages over a four-year period before eventually acquiring adult plumage and moreover have a non-breeding plumage.  Hybridization is common and can cause added confusion. Many shorebirds have extremely subtle differences in size, plumage and bills.  There are juvenile, breeding and non-breeding plumages.

Hummingbirds are hard to ID because not only do they move quite quickly, but depending on the light, the colors are hard to see.  Their feathers are iridescent as opposed to pigmented.  The brilliant metallic colors are the result of light reflection by the microscopic structure of the feather surface.  Often due to poor light, a hummingbird’s feathers—or some of them—will appear black.  Another problem occurs when they molt; a single tail feather on the Stripe-throated Hermit or the crest and/or “scarf” of the White-Crested Coquette may be absent, which leads to faulty IDs.We have a similar problem with diurnal raptors which may go through three changes of plumage.  Their wing and tail length sometimes varies with age, with the younger specimens having longer tails and wings. Serious variations of plumage exist within a single species from one region to another.

 3  4

 Long-billed Starthroat

 Tiny Hawk

Learning to ID flycatchers takes a lot of patience and some, including species from the entire genus Empidonax,  are impossible to ID without a song.   Here on the Osa there are many that have lightly-streaked breasts, gray heads, wing bars or margins with varying degrees of pronunciation.  Another group, commonly called Pecho amarrillo locally, have several variations not easily discerned by the novice to the tropics.  One has a forked tail, another rufous on the wing, one has a striped head and another an all gray, slightly-divided crest.

Additionally, there will be the odd birds with very abnormal colorations. One day, between the Rio Madrigal and Carate, we encountered an all-black bird with a totally white head. Our first thought was we were observing an undiscovered species.  Wrong!  We heard it call, and realized it was a Black-hooded Antshrike.  This strangely colored bird had partial albinism which follows feather groups, a not uncommon occurrence.  There are also individual birds that can have a diluted or pale plumage and others can be melanistic and exhibit an excess of black and brown pigments.

My favorite example of odd coloration, and rarer than the above conditions, is a parakeet that was moving with the Crimson-fronted Parakeets but with a completely red head. We looked in books to see if any species with nearby ranges had this coloration. We sent out photos to several world birders and they were stumped.  After a bit more than a week of observation of the group, we saw the odd bird change into the normal plumage of a Crimson-fronted Parakeet.


White-crested Coquette

There are few birders that could not improve their ID skills. Never be afraid to contradict another birder or comment as to other identification possibilities.  We all have different observation strengths and experiences and ALL birders make faulty ids occasionally. And please give careful thought to a potential rare bird sighting. If a birder feels he or she is seeing a rare bird or a specimen out of the normal range, photos should be taken along with extensive field notes and others should be asked to come verify the record.


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