the census plots during this study. Shorebirds 
dominated this group (six of seven species) even 
more strikingly than is the case at Barrow (seven 
of 11 species—Norton 1973). The two seasons, 
1971 and 1972, differed in weather: the first 
was comparatively mild with an early and regu- 
lar snowmelt, whereas the second was cold with 
a delayed and prolonged snowmelt. This differ- 
ence between seasons was reflected in delayed 
onset of nesting by most or all of the species, as 
indicated in Fig. 2. 
Overall nesting success (eggs hatched/eggs 
laid) was universally higher in 1972 (Table 2). 
This improvement may be related to a reduction 
in local arctic fox (Alopex lagopus) populations 
during the winter of 1971-72 through a deliber- 
ate trapping program conducted around Prudhoe 
Bay (W. Hanson, pers. comm.) to remove nul- 
sance animals attracted to refuse disposal areas. 
Foxes were observed more frequently on the 
plots in 1971 and were strongly suspected to be 
the major (if not sole) agents of nest predation 
that year. 
Nesting densities of Prudhoe Bay birds were 
lower than those of their ecological counterparts 
at Barrow (Table 3), with the exception of the 
semipalmated sandpiper (Ca/idris pusilla) and 
red phalarope (Phalaropus fulicarius). \t is very 
difficult, however, to circumscribe the appro- 
priate species as being ecologically equivalent in 
the two localities. Although the nine species 
listed in Table 3 are the major insectivores (and 
granivores) in each region, there are additional 
insectivorous species in the Barrow system, such 
as the ruddy turnstone (Arenaria interpres); 
129 
golden plover (Pluvialis dominica), and non-nest- 
ing long-tailed jaegers (Stercorarius longicaudus). 
These three species are omitted from Table 3 
because of their absence as significant elements 
at Prudhoe in 1971 or 1972. Their inclusion in 
this analysis would demonstrate more clearly the 
greater use of tundra arthropod resources by 
birds in the Barrow area. Data in Norton's 
(1973) bioenergetic studies of Barrow shorebirds 
may be used to estimate that insectivorous 
species there ingest some 4x10° kcal km-2 yr-! 
from the tundra arthropod resources. The same 
estimation procedure for Prudhoe Bay would 
probably put energy ingested by comparable 
members of the community at somewhat less 
than 75% of the Barrow system, or about 3x10° 
keal km-2 yr! in 1971 and 1972. 
Various inter- and intra-plot comparisons of 
census information may be used to discern the 
spatial and temporal patterns of resource use by 
Prudhoe Bay birds. For example, Plots A and B 
became snow-free early and approximately 
simultaneously each year, and bird counts 
dropped to less than 10% of peak abundance by 
late July on each plot. By contrast, Plot C was 
slower by 7-10 days to become snow-free in 
1972. Its bird populations remained at 20-25% 
of peak numbers until the end of July. This 
situation is parallel to that found in different 
plots at Barrow (Norton 1973, p. 21). Late 
season resource use seems to be concentrated on 
areas unavailable earlier in the season. Another 
way to demonstrate this assertion is to break 
down census information from Plot B by in- 
dividual rows within the plot (Figs. 3a, 3b, 4). 
Table 2 
Nesting densities (nests km°2) and hatching success (eggs hatched/eggs laid) by species and 
year at Prudhoe Bay. 
Year 1971 Year 1972 
Density Success Density Success 
Species (nests km?) (nests km’2) 
C. pusilla S7A 0.52 42.4 0.84 
P. fulicarius S751 0.31 22:2 0.83 
T. subruficollis 2.8 0.0 5.7 1.0 
C. alpina 4.3 0.0 5.0 1.0 
C. melanotos 5.7 0.33 5.7 1.0 
L. lobatus 4.3 0.33 5.7 1.0 
C. lapponicus 8.6 0.47 6.7 0.73 
Overall 99.9 0.38 93.4 0.86 
