A SOLO TRIP TO UJARRÁS; BANDING RUBY-THROATED HUMMINGBIRDS IN COSTA RICA

In November 2015 we took a solo hummingbird banding expedition to Ujarrás, Costa Rica; we were unable to recruit enough participants to take our usual group as part of Operation RubyThroat: The Hummingbird Project. The expedition was funded in large part by ORT alumni from our previous 25 trips; their names are listed at the end of the write-up. We were assisted by long-time colleague Ernesto M. Carman and by Paz Irola and Julio Madriz; the latterw as gracious enough to allow us to run mist nets in his family's Chayote field. Just below is a summary of what turned out to be a very productive trip.

All text, maps, charts & photos © Hilton Pond Center

1. On six field days in November 2014, the 11-member "HellBanders" team (plus leaders) of Operation RubyThroat helped catch, band, and release unharmed an unprecedented 131 Ruby-throated Hummingbirds (Archilochus colubris) at Ujarrás, Costa Rica; the team primarily used mist nets in commercial fields of Chayote (Sechium edule, fruit at right) and deployed five Dawkins-style traps baited with sugar water feeders at El Cas, an outdoor restaurant nearby. This year's captures brought our four-year total to 239 RTHU banded on Costa Rica's Caribbean slope--where they're "not supposed to be."
2. Ruby-throated Hummingbirds captured at Ujarrás in 2014 through Operation RubyThroat showed an interesting age-sex ratio similar to what we saw there in previous years, and that typically has occurred on our other Neotropical expeditions: Lots more males than females. This year 89 of 131 RTHU were immature males (68%) with partly red throats, 16 (12%) were adult males with full red gorgets, and only 26 (20%) were females (color marked female at right). We're still not sure what such a skewed ratio might mean, with these options as possibilities: 1) There may be a netting/trapping bias; 2) Females may be feeding on food sources other than Chayote; 3) Males may be more likely to explore new areas, thereby wandering into the Orosi Valley in greater numbers; 4) Females may not migrate as far south as Costa Rica, stopping instead in Mexico or a more northerly Central American country; and/or, 5) Something else entirely. (We welcome your own hypotheses explaining this phenomenon; send your ideas to us via INFO.)
3. The total of 131 Ruby-throated Hummingbirds captured in in Chayote fields in 2014 exceeded local totals from our 2011 (43 RTHU), 2012 (50 RTHU), and 2013 (15 RTHU) seasons COMBINED and surpassed the total for any of our 23 previous Operation RubyThroat expeditions to any country in Central America. All things in nature are cyclic, so it is difficult to explain our unprecedented success in 2014. We suspect one factor was that Chayote fields we had worked in previous years seemed to be past their prime and were not producing an optimum crop of nectar-rich flowers; this may have concentrated RTHU in the more fertile plot at Little Hell. It's also worth noting that pre-trip scouting did not reveal many RTHU in any of the Chayote fields, possibly meaning the hummers had just arrived during the week the HellBanders were present. Arrival dates may vary year-to-year due to weather factors along the migratory route.
4. Another factor that may have influenced our record-setting captures of Ruby-throated Hummingbirds was that in 2014 Chayote plantation workers employed an aggressive irrigation policy, spraying the field with water more frequently than in past years. This meant the HellBanders were required to move nets more often to stay out of the spray. It may be that nets in constantly changing locations made it more difficult for RTHU to notice and avoid them. (This policy also made it difficult for Gavin MacDonald, our certified Operation RubyThroat cartographer, to document ever-changing net locations during the week. Nonetheless, he succeeded.)
5. In November 2014 we had no Ruby-throated Hummingbirds return to Operation RubyThroat's Ujarrás banding site after a northbound migration. (With just 15 RTHU banded in 2013, odds were against returns in 2014.) In 2012 and again in 2013 we did have re-traps of a male from the preceding year; these were at El Cas, the outdoor restaurant in our Chayote plantation study site. Both were males with full red gorgets (right, with blue color mark); they complement our discovery of RTHU site fidelity at two sites in Guanacaste Province (western Costa Rica) and at Crooked Tree in Belize. Site fidelity is well-understood for RTHU on North American breeding grounds but was not known within the species' winter range until we were first to document this phenomenon in 2006 at an Aloe Vera plantation near Cañas Dulces, Costa Rica (ten miles north of Liberia).
6. Only 12 of 131 Ruby-throated Hummingbirds captured at Ujarrás in November 2014 showed any signs of molt in tail or primary wing feathers; all these must be replaced before the long migratory flight back north. This contrasts greatly with RTHU captured in western Costa Rica in February when most birds have wing molt well underway (above right). By comparison, nearly all ruby-throats captured in Belize in early March through Operation RubyThroat have already finished with flight feather molt--pretty important because by then at least some RTHU are already winging their way north for the breeding season. We did note that nearly every RTHU captured in 2014 at Ujarrás showed significant wear to white tips of their other tail feathers.
7. In addition to 131 Ruby-throated Hummingbirds banded at Ujarrás in November 2014 we mist netted and banded 105 individuals of nine other Neotropical migrant bird species: Tennessee Warbler (87); Yellow Warbler (10); Indigo Bunting (2); and one each for Northern Waterthrush (right), Prothonotary Warbler, Ovenbird, Mourning Warbler, Baltimore Oriole, and Summer Tanager.
8. In November 2014 the HellBanders team again helped document winter site fidelity of other Neotropical migrants at Ujarrás, including three Tennessee Warblers, two Yellow Warblers, and a Mourning Warbler (right)--all banded in 2013 and recaptured locally. TEWA and YEWA--as nectarivores--undoubtedly return because of abundant Chayote nectar; we're not sure what the draw might be for MOWA.
9. Through Operation RubyThroat in 2014 we mist netted but did not band a male Green Thorntail and a male Black-crested Coquette (below right). It is interesting we also captured a male of each of these rather uncommon species in 2013 in the Little Hell Chayote fields; it's possible these were the same individuals year-to -year. They were among the remarkable 16 hummingbird species captured in four years at Ujarrás. Altogether, team members and leaders have documented 27 of Costa Rica's 51 hummingbird species within the Chayote since 2011, making this locale what we believe is the densest concentration of hummer species within the country--and perhaps one of the most varied hummingbird assemblages in such a small area ANYWHERE in the Neotropics.
10. In addition to 239 Ruby-throated Hummingbirds banded at Ujarrás in 2011-14 we've banded another 798 in Guanacaste Province on that country's Pacific side. We also banded 143 RTHU in Belize, 62 in Guatemala, 15 in Nicaragua, and two in El Salvador for a total of 1,243 in the Neotropics since 2004. This far surpasses the 46 that had been banded on the species' wintering grounds in Mexico and Central America prior to our first Operation RubyThroat citizen science trip in 2004.
11. Since December 2004, our 24 Operation RubyThroat expeditions offered through Hilton Pond Center and Holbrook Travel (plus one independent trip by the master bander) have enabled us to involve 195 citizen scientists--U.S., Canadian, Swiss, and Costa Rican teachers, birders, and nature enthusiasts in our ground-breaking ornithological research. This on-going project has focused primarily on Ruby-throated Hummingbirds (adult male, right) in five of seven Central American countries where RTHU spend "the other half of their year," i.e., when they're not on breeding grounds in North America. (We are hoping to mount an expedition to Honduras in 2016, but Panama's very small RTHU population probably does not warrant an in-depth investigation.) Of our 195 trip participants, 25 have been on at least two trips and two "groupies" have been with us six times and to every country where we've worked! We are grateful for everyone's assistance and support; without them our on-going success at discovering secrets of Ruby-throated Hummingbird site fidelity, migration, foraging behavior, and population dynamics in the Neotropics would not have been possible. Most recently, we appreciate the hard work of our HellBanders '14 group, who raised the bar for what constitutes a "successful" Operation RubyThroat expedition.
12. On all our Neotropical trips we try to explain our hummingbird studies to local citizens, whether they be landowners, laborers, students, or residents who happen to walk by. After all, Operation RubyThroat researchers are guests in the Chayote, Aloe Vera, and Cashew farms where we deploy our mist nets, so it's only appropriate to acquaint our hosts with the significance of our banding work. For example, this year in Little Hell a local father and his son watched the banding table from afar until the master bander invited them over for closer view. The young boy (below) was fascinated by our procedures and had a exciting experience when he got to release a just-banded Yellow Warbler back into the wild. We suspect this is an opportunity the boy will not soon forget.

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