Date of Award
9-17-2014
Document Type
Thesis
Degree Name
Biology, MS
First Advisor
Thomas Risch
Committee Members
Aaron Pierce; Paul Sikkel; Richard Grippo; Virginie Rolland
Call Number
LD 251 .A566t 2014 F68
Abstract
The Isles Dernieres Barrier Island Refuge (IDBIR) represents an ecologically sensitive area that is historically important habitat for wintering and breeding waterbirds, and is currently threatened by habitat loss, disturbance, and climate change. The northern Gulf of Mexico coastal habitat is particularly important to colonial nesting waterbirds such as Black Skimmers (Rynchops niger), a representative species that relies on barrier island habitat for more than half their nesting grounds. Similar to that of many coastal birds, there is a paucity of information on skimmer foraging ecology, specifically what prey species they deliver to the nest and where they forage. This study employed colony surveys, nest daily survival rates, video recorders, video and GPS telemetry to gain new insight into reproductive and foraging ecology (including site selection, nesting effort, nest success, and foraging patterns) of skimmers on the IDBIR from 2011-2013. The refuge contains five barrier islands and, during each of the 3 successive years, Black Skimmers attempted to nest on four of the five islands. West Raccoon Island supported the largest colonies (550‒1,191 nests), followed by East Raccoon (48‒487 nests), and Wine Island (6‒55 nests). Successful nesting occurred only during 2011 and was restricted to two sites (West and East Raccoon Islands). Complete reproductive failure occurred at all sites in 2012 and 2013 due to flooding. During 2011, 61% of the 62 nests monitored hatched young successfully, while 34% of nests failed due to abandonment, predation, or flooding. Of the total 396 monitored nests in 2011 & 2013, 88% (353 nests) failed before hatching (68.75% flooding, 6.25% predation, 13.25% other causes). Skimmers fed young mostly at night (63% feedings occurred at night; n = 38) with a mean food provisioning rate of 2 fish per hour, each a single prey delivery. Females made more prey deliveries (66%) to nests than the males (n = 38 total feedings). In total, 67 skimmers were captured, 46 of which were equipped with radio transmitters. I recorded 203 radio locations, most of which were within 800 m of the colonies. Of these, 26 locations (10%) were documented at dusk and at night when skimmers are actively foraging. According to kernel density estimates, the mean home-range size was 50 ha and ranged from 10.62 to 243.78 ha (SD = 74 ha, n = 11). I determined that conventional VHF telemetry methods were biased and ineffective for tracking skimmer foraging movements because birds could not be detected beyond 800 m of nesting colonies, and therefore I used GPS data loggers in 2013. From one skimmer sampled with a GPS data logger, 15% of 202 locations were identified as foraging activity according to time of day and elevation. This male made 14 trips directly north of the breeding colony, and traveled a maximum distance of 16.4 km (mean = 8.3km, SD= 5.4 km) from the breeding colony. On average, this bird traveled 23.8 km for round-trip foraging trips (range 0.06-34.44 km). Finally, trapping methods provided a means of gathering information on selected prey species. In total, seven of 67 (10%) skimmers captured were carrying fish, which primarily included Pogie (Brevoortia partornus), Mullet (Mugil cephalus), and Silverside (Menida peninsulae). These data on movements and diet provide valuable insight into skimmer habitat use on the refuge, which may be representative for other skimmer colonies throughout the Northern Gulf of Mexico. More long-term data are needed on the reproductive output to evaluate skimmer population trends, threats, and future outlook for the species.
Rights Management
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Furfey, Brehan, "The Reproductive and Foraging Ecology of Black Skimmers (Rynchops Niger) On A Barrier Island Refuge in Coastal Louisiana" (2014). Student Theses and Dissertations. 783.
https://arch.astate.edu/all-etd/783
