Are there Fer-de-Lance on the Nicoya Peninsula ?

 Arguably Central America’s most deadly and widespread venomous snake is the Fer-de-Lance or Terciopelo. It can be found in a wide variety of habitats throughout Costa Rica.  Studies have even shown that it can survive -- and indeed thrive -- in disturbed habitats in close proximity to humans.

Fer-de-Lance (Bothrops apser)

The big "question mark" remains on the Nicoya Peninsula.  Although no confirmed records exist for the region, the thing I've learned over the years is that doesn't stop most people from believing they are here.

I actually still hold out hope that they do occur here; there is certainly suitable habitat at the southernmost tip in Cabo Blanco national park, but so far I have never seen one. I do however have an alternate theory of what people are seeing.  

Lyre Snake (Trimorphodon biscutatus)

 Fer-de-Lance (Bothrops apser)

The Lyre Snake (Trimorphodon biscutatus) is a common enough snake throughout the Peninsula in multiple habitats, and could very well be the infamous Nicoya Fer-de-Lances people are seeing. Here are a few reasons why: they have a very similar pattern - it’s not a distinct "X" pattern like the Bothrops, but it does overall have very similar coloration. Their behavior when first encountered is strikingly similar: in Panama I came upon a Fer-de-Lance moving along a bank side.  When it spotted me it quickly coiled up start rattling its tail on the leaf litter and brought its head up. I have witnessed the Lyre Snake do the exact same thing.  Now unlike the Fer-de-Lance it won’t make as tight of a coil or stay like that for long: they usually try the threatening position then scatter. The tail rattling though is the exact same in both, and for me it’s one of the more compelling similarities. If you only get a quick look the lyre snake will also flatten its head in a similar fashion to a pit viper. Their eyes can also fool you at first glance they can create a very narrow slitted iris similar to a pit viper.

The flat triangle shaped head distinct in Pit vippers.

If you were to take a close enough look though you would notice the lack of sensory pit glands that all pit vipers posses.

Sensory pit glands on the front of a Fer-de-Lance

So for now I’m still very skeptical that Fer-de-Lance occur widespread throughout the Peninsula, but I still very much hold out hope they are here and that I can finally confirm their occurrence here.

Big Trees, Kentucky Warblers, and Site Fidelity

La Reserva Natural Absoluta Cabo Blanco -- the Cabo Blanco Absolute Nature Reserve -- was Costa Rica's first national park.  The Reserve celebrated its 50th anniversary last year.  Before the land was preserved, the area was a hodgepodge of private farms and cattle ranches.  Now the 3,000 acres of forest protected at Cabo Blanco are a testament to the impressive speed at which tropical habitats can regenerate: its youth is masked by the presence of gloriously massive trees, including fast-growing giants such as Guanacaste (Enterolobium cyclocarpum) and Ceiba (the genus to which the mighty Kapok belongs).

This forest is the winter home of a number of neotropical migratory songbird species, which is the reason we find ourselves in this wonderful place.  Among them are several species whose numbers are apparently in acutely rapid decline, such as Kentucky Warbler, Worm-eating Warbler, Ovenbird, Wood Thrush, and Swainson's Thrush.  This week we captured all of these species except Ovenbird (although we did manage to capture one at Finca Pura Vida last week).  We also captured and banded two other neotropical migrant warblers: Chestnut-sided and Tennessee.

The most exciting capture of the week was a Kentucky Warbler, not only because of my personal annual sagas trying to spot them in New Jersey, or because they are threatened in the state, but because one of the Kentuckys banded late last year by my team at Cabo Blanco was just recaptured again on Monday, one year and eight days (and about two thousand miles) later.  It was an immature bird at the time of capture, meaning it celebrated its first birthday this past summer, after its first (hopefully successful) breeding season in North America.

Fortunately I keep my photos organized well enough to have located a photo I took of this very bird during last year's research expedition:

Kentucky Warbler when it was originally banded on
December 14, 2013 (© Tyler Christensen)

Same individual as pictured above when it was recaptured
on December 22, 2014 (© Tyler Christensen)

Birds banded in a previous season and re-encountered in a later one are called between-season recaptures, and are not rare occurrences here (at this point about one in ten birds we capture was banded by the team in previous seasons), but we capture Kentuckeys infrequently enough that this was our first between-season recapture of this species.

Recaptures such as this demonstrate winter site fidelity, or the tendency of a bird to return to the same winter territory year after year.  Many of the migrants we capture are site faithful, and recapture rates among our most common migratory species from one year to the next are roughly 18% for Tennessee Warblers, 20% for Prothonotary Warblers, and a whopping 26% for our Northern Waterthrushes!

As several recent studies have shown, winter site fidelity and winter territoriality (which are related) are, in at least certain species, linked to habitat quality - higher-quality habitats often have repeat customers who stake territorial claims within them.

Evidently the forests of the Cabo Blanco nature reserve are agreeable to at least one Kentucky Warbler, who elected to return to spend another winter.  This group of bird banders happens to have made a similar assessment.

Nocturnal Creatures (Part I: Pacific Screech-Owls)

Dusk falls quickly in the tropics, and with it comes a rapid transition between the activities of the diurnal and nocturnal fauna.  As darkness falls, the daytime animals take advantage of the last few minutes of fading light.  The last of the day's hummingbirds fill their stomachs with nectar before calling it a night; the howler monkeys bellow one last claim on their territories; and flocks of Tennessee Warbler settle in to roost, nudging and shouldering each other to vie for the best spot on the branch.  Around this time there is a small window, just before the real darkness sets in, in which the bats and owls leave their daytime roosts and begin their nightly routines.  These are the creatures to whom the night belongs.

© Tyler Christensen

Pacific Screech-Owls (Megascops cooperi, above) are perhaps the most common owls in Costa Rica, much like our Eastern Screech-Owls (Megascops asio) at home in New Jersey.  Both species are flexible in their habitats and diets, making them well-suited to thriving in areas with human habitation.  I photographed the owl pictured above on the grounds here at Finca Pura Vida just a few evenings ago.

For the past few nights we have been capturing owls for our research, applying the same method I used during Washington Crossing Audubon Society's Saw-whet Owl Migration Survey.  This method involves the use of several mist nets and an electronic audiolure that plays the male vocalizations of the owl species being targeted.  Ever curious, owls often come in to investigate and wind up in the nets.

© Tyler Christensen

Various research projects require the capture of owls for study.  Ours involves deciphering patterns by which these birds replace their feathers, and whether these patterns can be used to discern the age of a bird in question.  While this research may not be universally interesting (I can think of several people off the bat who were visibly regretful after asking for more detail), I do think we can all appreciate the spectacular encounters that happen to go along with it.

You cannot catch owls here without also catching bats, and catch them we did -- indeed, some were as large as the owls themselves.  Our encounters with these bats will be the topic of Part II of this post.

Herpetofauna of the Nicoya Peninsula

Our primary objective while were here in Costa Rica is focused on ornithology research, but that doesn't mean we don’t delve into other subjects.  Much is still unknown about the distribution and abundance of reptiles and amphibians here on the Nicoya Peninsula .  Over the past few years we have taken a lot of notes and data points on where we have found various species of snakes, lizards, frogs, and turtles across the Peninsula.   

As we've been going along, I've been using the Meet Your Neighbors photo studio technique to isolate subjects on completely neutral backgrounds. It serves a dual purpose of having very clear record shots, and also will hopefully go into a guide of sorts for the herpetofauna for the Peninsula at some point. 

Our first day came with an interesting discovery -- On our way from the ferry to the Finca, Tyler spotted something sliding back and forth across the road: a Green Ratsnake  (Senticolis triaspis). This Colubrid is in the same family as our Black Ratsnake at home, and they share very similar behavior and diet. 

Green Ratsnake  (Senticolis triaspis)

 

 

Later on in the first night as we were walking around the Finca, Tyler spotted something on the side of one of the buildings. It was a large frog, apparently scanning the property from a high perch. We quickly grabbed a butterfly net and lowered him down for identification.  It turned out to be the ever-interesting Common Milk Frog (Trachycephalus venulosus). These frogs can secrete a noxious mucus-like chemical from their skin when disturbed.   

Common Milk Frog (Trachycephalus venulosus)

 

The latest species we encountered was Costa Rica's poster-child of fauna, the Red-eyed Tree Frog (Agalychnis callidryas).  We had heard them in the past at the Finca, but could never locate them. The other night, we set out on a mission to finally locate them and get photographic documentation. After what some might call an intrepid adventure, we located between 6-7 individuals.  As you can see, it was well worth it -- "charismatic" doesn't even begin to describe these frogs. Interestingly enough, they are very variable in coloration, depending on if you’re on the Pacific or Caribbean side of Costa Rica.  The frogs from the Caribbean side are more colorful, but the Pacific variant has their own unique charm. 

Red-eyed Tree Frog (Agalychnis callidryas)

Warm Greetings

A trio of Mangrove Swallows (tropical relatives of our Tree Swallow) was swirling behind the ferry that crosses the Gulf of Nicoya, showing off the impressive aerobatic skills shared by all members of the swallow family.  Brown Pelicans travelled low in formation over the water.  Magnificent Frigatebirds, fork-tailed and long-winged wanderers of the open ocean, circled higher, watching and waiting to steal the hard-fought-for meal of a Laughing Gull or Royal Tern.  The occasional Brown Booby would cross in front of the ship.

Brown Pelicans aboard a small fishing boat in the Gulf of Nicoya

Our arrival in Costa Rica yesterday marks the beginning of the fourth annual research expedition of the Nicoya Peninsula Avian Research Station.  In each of these four years my research partner Sean Graesser and I have traveled to the Nicoya Peninsula of the northwestern portion of the country to collect important data on some of the more vulnerable species of neotropical migratory songbirds, which spend their winters here.  Over the next seven weeks we will run several bird banding stations to capture, mark, and study these long-distance migrants, and to collect data from individuals that we banded in the past that have returned.

The sun was going down as we turned down the dirt road that leads to Finca Pura Vida, the farm on which we will live for the next two months.  As we tried (in vain) to dodge the myriad potholes, two bird calls familiar to us northerners came through the open windows: the "stchip" of a Yellow Warbler and the “kinkachurr” of a Summer Tanager.  I welcomed these as warm greetings to our return to Costa Rica.  It’s good to be back!

Season Highlights

Although it certainly doesn't feel like it, a full month has gone by since the NPARS team returned to North America from its latest excursion to the American tropics.  For seven weeks, our team of volunteer researchers lived and worked on the Nicoya Peninsula of northwestern Costa Rica collecting important data on neotropical birds.  To officially close the research season, I'd like to look back at some of the highlights of the trip, including some of my favorite photos of and encounters with birds and other wildlife.

American Crocodile (Crocodylus acutus) near our banding site at Refugio Curu

Scarlet Macaw

This Crab-eating Raccoon (Procycon cancrivorus) paid the
banding station at Refugio Curu a visit just after Christmas

Occasionally we would have slow days at the banding station, which would give us opportunities to divert our attention to things other than birds.  No matter how much time we devote to looking, the tropical forests of Central America never fail to offer something exciting and new - especially when we turn our attention to the small and easily-overlooked.

Nogodinid Planthopper Nymph

Occasionally we encountered the remarkable-looking planthoppers of the family Nogodinidae.  Nymphs of these planthoppers grow long, waxy filaments that resemble optical fiber from the tips of their abdomens.  This feature has earned such nymphs the informal nickname "fluffy bums".  The exact function of these wax-like filaments remains unknown, although they may provide a defense somewhat like the detachable tails of lizards and geckos; an attacking predator may end up with a mouthful of wax rather than the insect itself.  If disturbed, these planthoppers will catapult themselves into the air with an audible 'POP'.

Dead Leaf Katydid (Mimetica sp.)

Bark Mantis (Liturgusa sp.)

Caterpillar 'feet' (Automeris sp.)

A lot of people have been asking me how we get the shots with white backgrounds; the method used involves photographing subjects on a sheet of translucent white plastic, which is illuminated from above and below using remote-controlled flashes.  The goal is to have an evenly-lit subject on a perfectly white background, free of shadows.  I'm an amateur when it comes to this mode of photography, and experienced photographers can have much more elaborate (and innovative) studios.  Twan Leenders, president of the Roger Tory Peterson Institute, constructed a field studio from the back of his rental car while he was visiting the banding stations, and used it to photograph banded birds prior to their release.

Twan Leenders photographing birds in a field studio

Prothonotary Warbler - Photograph © Twan Leenders; used with permission

The team completed its third unofficial Christmas Bird Count on January 11th.  Since there is no official Audubon Count Circle in this region of Costa Rica, we decided to make this year's bird count purely a numbers game with the object of seeing as many species as possible.  This sort of birding has little scientific value, but it's a great way for the team to take a break from research, practice their identification skills, and have a great deal of fun.  After a session of serious strategizing at the Finca the night before, we had laid out an agenda for the following day to cover as many habitats as possible and maximize our species potential.

Chestnut-sided Warbler

Snowy Egret at the ferry in Paquera

We birded for nearly twelve hours, and had visited sites along the entire eastern coast of the Peninsula.  By the end of the day we had a total of 128 species, just seven species behind last year's high count of 135.  Just like last year, the final species of the day was a Pacific Screech-Owl singing in the yard at Finca Pura Vida just after dark.

Pacific Screech Owl, # 128 on our Christmas Bird Count

Most reptiles and amphibians are active at night, making this the best time to find them.  We spent several late nights cruising the roads after dark, which is a good way to cover a lot of ground and spot critters more easily against the asphalt.

On a particularly slow evening, when we were about to turn the car around and call it a night, "WHAP!" - something large, about the size of a baseball, fell 40 feet from the trees above the road and landed on the car.  When we stopped to look, attached to the passenger-side mirror was Costa Rica's largest tree frog, the Veined Tree Frog (Trachycephalus venulosos).  This species can, when disturbed, secrete copious amounts of a sticky, irritating milky liquid (hence its Spanish common name Rana Lechera, or Milk Frog).  Incredibly, the frog remained healthy and intact after its encounter with our car.

Veined Tree Frog (Trachycephalus venulosus)

During a two-day visit to the Karen Mogensen Reserve in the mountains of the Nicoya Peninsula, we found, among other things, a gorgeous Tropical Kingsnake (Lampropeltus triangulum); these snakes are spectacular mimics of the venomous Coral Snake (genus Micrurus).  Although kingsnakes are completely harmless, their strong resemblance to the "real thing" causes most would-be predators to opt out.  Even though we have both Kings and Corals here on the Nicoya Peninsula, this was our first encounter with L. triangulum since we began the project.

Tropical Kingsnake (Lampropeltus triangulum), a convincing Coral Snake mimic

The author with a Coral Snake in 2012; photograph © Jared Flesher

Hummingbirds aren't the only creatures that enjoy our nectar feeders at Finca Pura Vida; after dark, nectar-feeding bats come in droves to sip sugar water.  One night when we had the mist-nets open at the feeders to capture and photograph bats, we had an incidental capture of an insectivorous (insect-eating) species we'd never seen before, the Black-winged Little Yellow Bat (Rhogeessa tumida).  "Little" seems to be an understatement, as this bat was minuscule, about the size of a hummingbird.

Black-winged Little Yellow Bat (Rhogeessa tumida)

We also found that it was carrying a tiny hitchhiker called a Flat Fly, a type of parasitic fly that we find often on birds in North America.  As their name suggests, Flat Flies (Family Hippoboscidae) are dorsally compressed, allowing them to navigate the spaces between feathers or fur with unsettling speed, thereby avoiding the beaks, claws, or teeth of their hosts while they groom themselves.  Most species are host-specific, meaning they may only be found on one, or at most few, host species.

Flat Fly (Hippoboscidae) found on the
tail membrane of Rhogeessa tumida

Even after some editing, I have nearly 10,000 photos from the trip.  For my parting shot, I discreetly took this photo of NPARS's co-director Sean Graesser and banding technician Benny Jacobs-Schwartz photographing birds near Monteverde.  It's hard to convey these seven weeks of experience in one blog post, and harder still to articulate just how special this area of the world is; but if I had to try using a single photo, it would be this one:

2013 - 2014 Banding Totals

We spent 18 days banding between our sites at Reserva Nacional Cabo Blanco and Refugio de Vida Silvestre Curu.  During that time we banded 281 birds (192 residents and 89 neotropical migrants), processed 60 that were originally banded by us either in 2011/2012 or 2012/2013 (38 residents and 22 neotropical migrants), and released 42 individuals (almost all resident hummingbirds) without bands.  Of all the birds captured, 29% (111 individuals) were neotropical migrants, which was slightly higher than last year's 24%.  During our three years at these sites the proportion of residents to migrants has consistently been close to 3:1.  

Additionaly, 20% of the migrant species we captured were birds that we had banded in previous years; these are birds that have traveled to breeding sites in North America and then back again, returning to the exact same wintering territories.  In fact, several of them were caught in the same net!

Prothonotary Warbler at the banding station at Refugio Curu

MIGRANTS:

Our most commonly encountered neotropical migrants this year were Northern Waterthrush (N = 35), Tennessee Warbler (N = 26), and Prothonotary Warbler (N = 12).  Other notable captures included a relatively high number of Philadelphia Vireos, a single male Painted Bunting, and a recapture Wood Thrush; the latter was originally banded on December 19th, 2012 as a first-year bird.  Although we capture Wood Thrushes occasionally, this individual, now in its third year, is the first Wood Thrush that we have encountered in successive seasons.  The reason that encounters with this species are particularly exciting for us is that Wood Thrushes, according to the literature currently available, are not "supposed" to overwinter in this region of Costa Rica.  We believe, and such encounters strongly support, that Wood Thrushes do regularly overwinter in the region, albeit in small numbers.

Nicole Guido with two Wood Thrushes; the bird on the right was banded in 2012.

First-year male Prothonotary Warbler

Second-year Northern Waterthrush

Neotropical Migrant Banding Totals, 2013/2014 
111 (89 new, 22 recapture)

	New
23	Tennessee Warbler	1	Worm-eating Warbler
21	Northern Waterthrush	1	Painted Bunting
9	Prothonotary Warbler	1	Dusky-capped Flycatcher
7	Philadelphia Vireo	1	Swainson’s Thrush
5	American Redstart
4	Ovenbird		Recaptures
3	Chestnut-sided Warbler	12	Northern Waterthrush
3	Wood Thrush	3	Tennessee Warbler
3	Summer Tanager	3	Prothonotary Warbler
2	Yellow-bellied Flycatcher	1	Wood Thrush
2	Kentucky Warbler	1	Dusky-capped Flycatcher
2	Yellow Warbler	1	Chestnut-sided Warbler
1	Great-crested Flycatcher	1	Philadelphia Vireo

RESIDENTS:

Our most common resident species was, by far, Long-tailed Manakin (N = 59).  Trailing not-too-closely behind were Clay-colored Robin (N = 22), Black-headed Trogon (N = 16) and Gray-headed Tanager (N = 15).  Long-tailed Manakin has been our most common resident species every year, but this year the margin was staggering.  New species to our banding stations this season were Common Paraque, Hoffmann's Woodpecker, and Olive Sparrow.

Benny Jacobs-Schwartz with an adult Long-tailed Manakin

Sean Graesser with a pair of Turquoise-browed Motmots

Green Kingfisher

Resident Banding Totals, 2013/2014

230 (192 new, 38 recapture)

	New
49	Long-tailed Manakin	1	Hoffmann’s Woodpecker
21	Clay-colored Robin	1	Greenish Elaenia
14	Black-headed Trogon	1	White-collared Seedeater
12	Gray-headed Tanager	1	Yellow-throated Euphonia
9	Ruddy Woodcreeper	1	Streaked Flycatcher
6	Olivaceous Woodcreeper	1	Boat-billed Flycatcher
6	American Pygmy-Kingfisher	1	Blue-crowned Motmot
6	Rufous-and-white Wren	1	Blue-black Grassquit
5	Red-crowned Ant-Tanager	1	Common Paraque
5	Lesser Greenlet	1	Barred Antshrike
4	Great Kiskadee	1	White-tipped Dove
4	Streak-headed Woodcreeper
4	Ivory-billed Woodcreeper		Recaptures
3	Rufous-capped Warbler	10	Long-tailed Manakin
3	Mangrove Vireo	5	Rufous-and-white Wren
3	Yellow-olive Flycatcher	4	Olivaceous Woodcreeper
3	Bright-rumped Attila	3	Gray-headed Tanager
3	Northern Barred-Woodcreeper	3	Barred Antshrike
3	Green Kingfisher	2	Black-headed Trogon
3	Slate-headed Tody Flycatcher	2	Rufous-capped Warbler
2	Rose-throated Becard	2	Stub-tailed Spadebill
2	Olive Sparrow	1	Bright-rumped Attila
2	Plain Xenops	1	Plain Xenops
2	Blue-black Grosbeak	1	Ruddy Woodcreeper
2	Stub-tailed Spadebill	1	Blue-crowned Motmot
2	Turquoise-browed Motmot	1	Greenish Elaenia
2	Rufous-naped Wren	1	Clay-colored Robin
1	Long-billed Gnatwren	1	Yellow-olive Flycatcher­

HUMMINGBIRDS:

At our new hummingbird banding station at Finca Pura Vida we processed 188 hummingbirds of 11 different species; 176 of these were new, and 12 were recaptures from last year.  Our most common humminbird (again, with a significant margin) was Green-breasted Mango (N = 68), followed by Steely-vented Hummingbird (N = 28) and our migratory Ruby-throated Hummingbird (N = 21).

Immature male Ruby-throated Hummingbird

Adult male Green-breasted Mango

Perhaps the most exciting species on this list are the Long-billed Starthroat and the White-necked Jacobin; if you followed our updates from last year's study season, you may remember that neither of these species is "supposed" to occur on the Nicoya Peninsula, and yet they make regular appearances at the feeders at Finca Pura Vida.  Since we began banding hummingbirds last winter, we have captured 5 White-necked Jacobins and 6 Long-billed Starthroats.  Is their presence on the Peninsula only seasonal?  Do they undergo a short-distance migration during the non-breeding season?  Or is there a small breeding population present year-round that has yet to be confirmed?  Further study may reveal the answer.

Female (left) and male (right) White-necked Jacobin

Finca Pura Vida: Hummingbird Banding Totals, 2013/2014

188 (176 new, 12 recapture)

	New
68	Green-breasted Mango	1	Stripe-throated Hermit
28	Steely-vented Hummingbird
21	Ruby-throated Hummingbird		Recaptures
16	Rufous-tailed Hummingbird	1	Blue-throated Goldentail
10	Blue-throated Goldentail	2	Cinnamon Hummingbird
10	Scaly-breasted Hummingbird	1	Green-breasted Mango
8	Cinnamon Hummingbird	1	Plain-capped Starthroat
6	Plain-capped Starthroat	5	Rufous-tailed Hummingbird
4	Long-billed Starthroat	2	Steely-vented Hummingbird
4	White-necked Jacobin

Overall 2013/2014 was a productive season for NPARS; between the new and recaptured birds at Cabo Blanco, Refugio Curu, and our hummingbird banding station at Finca Pura Vida, we processed a grand total of 529 birds, which included three species that were entirely new to our banding stations.

That's it for the numbers - our next post will consist of slightly lighter fare, with photos and anecdotes covering our favorite experiences from our six weeks in Costa Rica.