|
|
|
|
SITE NAME
|
|
Canning River Delta, Arctic National Wildlife Refuge, Alaska, USA
|
|
| Contact details
(phone/fax//e-mail//address): |
| (907) 456-0303/(907) 456-0428(fax) // Steve_Kendall@fws.gov // U. S. Fish and Wildlife Service, Arctic National Wildlife Refuge, 101 12th Ave., Room 236, Fairbanks, AK 99708, USA
|
|
PROJECT DETAILS |
|
Project name:
|
|
Nest survival of tundra-nesting birds relative to human development on Alaska's Arctic Coastal Plain
|
|
|
Start of survey:
|
End
of survey: |
Team
size: |
|
5.06
|
14.07
|
6
|
|
WEATHER
CONDITIONS
|
|
|
|
Weather conditions: |
| This was our 5th year at the study site and the earliest melt observed thus far. There also was an early snow melt in 2002, but not quite as early as 2006. Snow completely melted beffore 5 June.
|
|
|
|
|
|
|
|
| Date of ice-break on
rivers: |
|
|
| Date of final loss of
snow: |
|
|
BIOTIC
CONDITIONS
|
| Rodents abundance evaluation: |
high
|
|
|
Breeding conditions:
|
Conditions at the Canning River Delta in 2006 were atypical compared to the previous 4 years. Snow melt was early, and small mammal and predator abundance were higher than previously observed. In 2006, we found two Snowy Owl nests and four Pomarine Jaeger nests, but suspected that several more were present. Total predators observed during predator surveys were also higher in 2006 compared to all other years, due primarily to the higher abundance of Pomarine Jaegers. In addition there were at least three Arctic Fox dens at the study site, one with nine cubs. A commonly held assumption is when small mammals are abundant, predators switch their focus away from birds resulting in higher nest success. This was not true at the Canning River Delta in 2006. For all nesting species nest survival in 2006 was much lower than most of the previous years. Mayfield estimate of nest success was 0.022 in Dunlin (n=5), 0 in Pectoral Sandpiper (n=13), 0.126 in Semipalmated Sandpiper (n=16), 0.193 in Stilt Sandpiper (n=5), 0.118 in Red Phalarope (n=13), 0.023 in Red-necked Phalarope (n=23) and 0.037 in Lapland Longspur (n=73, including incubation and nestling stages). It appears that benefits of a higher mammal prey base may have been offset by the higher predator abundance.
At the Canning River Delta in 2006 we located and monitored 180 of nests of 12 species. The most abundant shorebird species were Semipalmated Sandpipers (density = 16.0 nests/km2) and Red-necked Phalaropes (density = 11.5 nest/km2). This was the highest density we have observed for Red-necked Phalaropes at the study site, which was not surprising as higher abundance of phalaropes are expected in years of early snow melt. However, Red Phalaropes nesting density in 2006 was much lower than in 2002, an early snow melt year with the highest density observed for this species at the study site. In 2006, Pectoral Sandpipers had the lowest nest density observed for that species (6.5 nests/km2) at our site.
|
|
|
Rodent dynamics:
|
| We do not have a reliable measure of small mammal abundance other than observational data and the presence of nesting Snowy Owls and Pomarine Jaegers (both species usually only nest in high lemming years). Observations of small mammals were at least an order of magnitude higher in 2006 than the previous 2 years (when we also quantified observations), and anecdotal observations 2003 and 2002 indicate small mammal abundance was relatively low in those years.
|
|
Rodent species recorded:
|
| Latin | Abundance |
|---|
| Lemmus trimucronatus | abundant |
| Dicrostonyx groenlandicus | rare |
| Microtus oeconomus | rare |
|
|
|
Summary
of fauna studies: |
Since 2002, the Arctic National Wildlife Refuge has worked with several partners to investigate the relationship between nest survival of tundra-nesting birds and predator populations on Alaska's Arctic Coastal Plain (ACP). We hypothesized that the dynamics of this relationship are affected by human development. The ACP is an important breeding site for many species of birds, several of which are declining. In the past several decades there has been increased development in this region, primarily associated with oil exploration and extraction. Some of the breeding bird populations may be vulnerable to effects of this development, including enhancement of predator populations. Development may cause changes in distribution or population size of nest predators by providing artificial food sources, nest/den sites, and surveillance roosts. Predation on the breeding grounds has been hypothesized to be the main source of population regulation for many bird species. Therefore, changes in predator distribution or density may have adverse population-level effects on tundra-nesting birds. Relationships between development, predator populations, and nest survival are not well documented for the ACP, however.
As part of this collaboration field studies were conducted at the Canning River Delta on the Arctic NWR from 2002 to 2005. During these studies we found considerable annual environmental variability, resulting in natural variability of nesting ecology, nest survival and predator abundance. Due to its location relative to existing oil field infrastructure on the ACP, the Canning River Delta would likely be one of the first areas impacted if oil exploration and development were to occur on the Refuge. This site could also be impacted by development of nearby gas fields at Pt. Thompson. Adequate baseline data for bird populations on the Delta will be vital to evaluate impacts of future activities and to develop appropriate mitigation strategies if necessary. We continued field studies in 2006 at the Canning River Delta and our partner, the Wildlife Conservation Society, conducted studies at Prudhoe Bay and Teshepek Lake. These efforts were done in order to increase our sample size and to facilitate statistically valid comparisons between sites and years.
Data from the larger study have been pooled and analysed by an independent statistician, using a spatially adjusted proportional hazards survival model with covariates for distance to and density of infrastructure, predator abundance, and nest site habitat to compare nest survival relative to human developed areas. The partners are now working on a manuscript for submission to a professional journal.
|
|