American
Robin
American
Robin was recorded on all 44 counts (Figure 8). It is far more numerous in
most winters than the other species considered here. It is unknown how many
robins might be year-round residents in the circle, but based on numbers of
breeding birds, any resident population would be of moderate size at best.
Robins occur throughout the circle and in varied habitats during winter, but
are much more numerous in the forest and woodland habitats of mountain areas
and coastal canyons than elsewhere. There they feed on fruits in orchards,
and on berries of madrone, and toyon. Numbers are most variable in the suburban
lowlands, where flocks are attracted to ripe berries of pyracantha, cotoneaster
and other exotic plants. During irruption years robins are typically common
in all areas, but very abundant in the forested inland portions of the circle.
Figure 8. American Robin on the Santa Cruz County CBC, 1957-2000.
Raw counts ranged from 74-18,050 birds. Irruptions (counts >150% of the standardized average, 23.4 per party hour) were recorded in nine years (20%): 1959, 1968, 1970, 1975, 1977, 1981, 1987, 1992 and 1996. Counts >100% of average occurred in 11 years (25%), and counts <25% of average occurred in 10 years (23%). All the major irruption years recorded on the count have been followed by years of much lower abundance (Figure 8).
Numbers on the five neighboring counts were moderately well correlated during
the 16 years examined, particularly in years of high and low regional abundance
(Figures 9 and 10). Not all circles had high relative abundance in the same
years (Figure 10). Santa Cruz County (avg 18.2 per party hour) and Palo Alto
(avg 10.4) had the most robins, with Santa Cruz County having peak abundances
far greater than those of the neighboring counts (Figure 9). Both these circles
have much greater areas of mixed broadleaf evergreen forest with abundant
madrones than occur in the other neighboring circles. Robins were less numerous
at Moss Landing (avg 6.6), Año Nuevo (avg. 5.3), and Monterey Peninsula
(avg 4.2).
Figure
9. American Robin on the five neighboring counts, 1983-84 to 1999-2000.
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Year
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Count
Circle
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Año
Nuevo
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Palo Alto
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Santa Cruz
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Moss Landing
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Monterey
Peninsula
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Legend
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0-50%
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51-100%
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101-150%
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>150%
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Figure 10. Comparison of American Robin annual abundance among the neighboring counts as measured by % of each count s average. (Note: for year, "83" = "83-84", "84" = "84-85," etc.; n.d. = no data.)
Varied
Thrush
Varied
Thrush was recorded on 43 of 44 counts (98%), but only one to five individuals
were found on four counts (Figure 11). A very small breeding population of
Varied Thrushes has been noted in the Santa Cruz Mountains from 1991 to the
present (not yet confirmed to nest in the count circle), but it is unknown
if they are year round residents. The winter population is presumed to be
all or nearly all migrants from the north. Varied Thrush occurs primarily
in areas of dense redwood forest and mixed broadleaf evergreen forest, especially
where trees are mature and large. Their retiring nature makes them difficult
to detect, although their vocalizations often betray their presence. Some
of the largest numbers have been tallied while driving quiet, forest roads
at first light, when the thrushes are often foraging along the roadway. This
species is often nearly absent in the coastal lowlands, except for small numbers
found in dense riparian or live oak woodland. Numbers in the lowlands may
increase during irruption years, but even then most Varied Thrushes are found
in forested mountains and valleys.
Figure 11. Varied Thrush on the Santa Cruz County CBC, 1957-2000.
Raw counts ranged from 0-1,022 birds. Irruptions (counts >150% of the standardized average, 1.2 per party hour) were recorded in seven years (16%): 1968, 1977, 1981, 1983, 1987, 1994 and 1998. Counts >100% of average occurred in 12 years (32%), and counts < 25% of average occurred in 15 years (34%). All the major irruption years recorded on the count have been followed by years of much lower abundance (Figure 11).
Cedar
Waxwing
Cedar Waxwing was recorded on 43 of 44 counts (98%), being missed on only the first count (Figure 12). Waxwings are non-breeding season visitors in the count circle, present from late August to early June. They occur throughout the circle and in varied habitats during winter. They are often relatively numerous in the extensive mixed forest and woodland habitats of mountain areas and coastal canyons, but may also be numerous in the suburban areas and parks of the developed coastal lowlands. They feed on fruits in orchards, and on berries of madrone, and toyon. In the suburban lowlands flocks are attracted to ripe berries of pyracantha, cotoneaster and other exotic fall and winter fruiting plants, as well as flowering blue gum eucalyptus. In some years they are rather locally distributed, with numbers concentrated in small areas of the circle. During irruption years they tend to be widespread throughout the circle, except at the coastal lowlands northwest of Santa Cruz.
Figure 12. Cedar Waxwing on the Santa Cruz County CBC, 1957-2000.
Raw counts ranged from 0-2,360 birds. Irruptions (counts >150% of the standardized average, 3.67 per party hour) were recorded in seven years (16%): 1959, 1968, 1975, 1977, 1987, 1990 and 1996. Counts >100% of average occurred in 16 years (36%), and counts < 25% of average occurred in 5 years (11%). Most major irruption years recorded on the count have been followed by years of much lower abundance (Figure 12).
Red
Crossbill
Red Crossbill was recorded on 25 of 44 counts (57%, Figure 13). Its somewhat more regular presence on the count from the 1970s onwards probably reflects improved coverage of its favored haunts and improved birding knowledge. Crossbills are found unpredictably in any season Santa Cruz County, but they are most frequently present during the fall and winter months. Sporadic breeding has been recorded in all seasons, and may occur with some regularity during major irruption years. In most winter seasons crossbills are sparse and very locally distributed, or absent. They occur generally throughout the forested areas of the circle, but are most consistently found in areas with Douglas fir, ponderosa pine or Monterey pine. Seed crops in these species vary from year to year, and crossbill distribution in the circle varies accordingly. During irruption years they are concentrated where these trees provide good foraging opportunities, but may also be found widely in areas with knobcone pine and where various exotic conifers are planted in the suburban coastal lowlands.
Figure 13. Red Crossbill on the Santa Cruz County CBC, 1957-2000.
Raw counts ranged from 0-275 birds. Irruptions (counts >150% of the standardized average, 0.22 per party hour) were recorded in seven years (16%): 1958, 1960, 1969, 1984, 1987, 1993 and 1996. As described for the nuthatch, rainy conditions on the 1996 count (during a major regional irruption) likely inhibited detection of this species. Counts >100% of average occurred in 9 years (20%), and counts < 25% of average occurred in 30 years (68%). All major irruptions years recorded on the count have been followed by years of much lower abundance (Figure 13).
Numbers
on the five neighboring counts were strongly correlated during the 16 years
examined (Figures 14 and 15). Año Nuevo (avg 0.51 per party hour) and
Santa Cruz County (avg 0.33) had the most crossbills, probably due to the
greater extent of potential habitat, especially forest with Douglas fir, which
is locally distributed or absent in the other circles. Crossbills were notably
less numerous at Moss Landing (avg. 0.09), Monterey Peninsula (avg 0.08) and
Palo Alto (avg. 0.04). The relatively low numbers at Monterey Peninsula are
surprising given the extensive Monterey pine forest in that circle.
Figure 14. Red Crossbill on the five neighboring counts, 1983-84 to 1999-2000.
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Year
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Count
Circle
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Año
Nuevo
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Palo Alto
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Santa Cruz
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Moss Landing
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Monterey
Peninsula
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Legend
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0-50%
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51-100%
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101-150%
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>150%
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Figure 15. Comparison of Red Crossbill annual abundance among the neighboring counts as measured by % of each count s average. (Note: for year, "83" = "83-84", "84" = "84-85," etc.; n.d. = no data.)