California Partners in Flight Coastal Scrub and Chaparral Bird Conservation Plan
Nuttall's White-crowned Sparrow (Zonotrichia leucophrys nuttalli)
Photo by Eric Preston
Prepared by: Ann Graham and Nellie Thorngate (firstname.lastname@example.org)
Ventana Wilderness Society's Big Sur Ornithology
Lab HC 67 Box 99
Monterey, CA 93924
Graham, A. and N. Thorngate. 2005. Nuttall's White-crowned Sparrow
nuttalli). In The Coastal Scrub and Chaparral Bird
Conservation Plan: a strategy for protecting and managing coastal scrub and
chaparral habitats and associated birds in California. California Partners
in Flight. http://www.prbo.org/calpif/htmldocs/scrub.html
action plan summary
Z. l. nuttalli is one of five subspecies of White-crowned Sparrow Zonotrichia leucophrys found in North America, and is the only subspecies found exclusively in California. It inhabits a narrow band along the California Coast from northwestern California to Santa Barbara County, California.
Other subspecies distributions are as follows (Chilton et al. 1995): Z. l. leucophyrys is found in northern Ontario, Quebec, Newfoundland, and northeastern Manitoba. Z. l. gambelii inhabits Alaska, the northern mainland of Canada, eastern British Columbia, and southwestern Alberta. Z. l. oriantha is found in mountainous western Alberta and western United States Z. l. pugetensis can be found along the Pacific Coast of North America ranging from Campbell River, Vancouver Island through northwestern California.
Currently, Z. l. nuttalli does not have any state or federally listed conservation status.
Z. l. nuttalli are permanent residents of a narrow fog belt found along the California coast from the northwestern edge south to Santa Barbara County (Mewaldt and King 1977).
CURRENT BREEDING DISTRIBUTION:
There have been no recent studies updating the distribution of Nuttall's White-crowned Sparrow.
AVERAGE TERRITORY SIZE:
Mean size of territory is 1,127 m2. Pairs with at least one successful fledgling have larger territories than unsuccessful pairs (2,760 m2 vs. 1,770 m2), and first-year males generally have significantly smaller territories than older males (1,640 m2 vs. 3,460 m2) (Ralph and Pearson 1971).
TIME AND OCCURRENCE OF SEASONAL MOVEMENTS:
Z. l. nuttalli is the only subspecies of White-crowned Sparrow that is entirely sedentary, and therefore does not migrate to breeding grounds.
EXTENT OF WINTERING IN CA:
As stated above, Z. l. nuttalli as a subspecies are residents of the
California coast year-round. Pairs will stay near one another throughout the
winter on or near their established territories and immature Z. l. nuttalli
will flock in groups of 3-10 individuals, mixing with Z. l. pugetensis
and Z. l. gambelii subspecies and Golden-crowned Sparrows (Mewaldt 1964).
Z. l. nuttalli utilizes a variety of strategies to feed. These include scavenging directly on the ground's surface, leaf-scratching on the ground, or foraging for insects in vegetation, rocks and the bark in the lower limbs of trees. They also are known to hawk insects from perches, as well as flycatch (Chilton et al. 1995).
Z. l. nuttalli forages for seeds that can include weed seed or small grains like oats, wheat, barley or corn, and other plant material such as grass blades or fruit, including elderberries or blackberries. Along with the plant material consumed, Z.l. nuttalli also eat insects including Hymenoptera, Coleoptera, and especially larval Lepidoptera. Animal matter consumption increases by as much as 125% from April through August (Chilton et al. 1995).
Standing or running water is typically found within or near a territory (DeWolfe and DeWolfe 1962).
BREEDING HABITAT:Since Z. l. nuttalli reside along the California coast, much of the breeding habitat, when not found in urban areas, is coastal chaparral. Features within a given territory include grass for rapid protective covering while foraging; bare ground for foraging; shrubbery to shelter a nest or provide a roost; and a source of water (salt or fresh). The combination of these elements works best when they are found in a patchy array so as to maximize territory suitability. Within a given territory, however, elements such as bare ground or water might not be immediately present, but may be found nearby (Chilton et al. 1995, DeWolfe and DeWolfe 1962).
Within coastal chaparral habitat, the shrubs most commonly used for nesting include baccharis (Baccharis), sage (Artemesia), Haplopappus, Rhus, Mimulus, and berry brambles (Rhubus) (Kern 1984, Petrinovich and Patterson 1983). In urban areas Z. l. nuttalli are more varied regarding choice of shrub, which may include non-native exotic shrubs (Blanchard 1941).
The bases of the nests are composed of small sticks, grasses, dead leaves, pine needles, and moss. The cup is lined with soft grasses, flower heads, hairs, duff, and leaves (Chilton et al. 1995, Kern 1984, Blanchard 1941).
HEIGHT OF NEST:
Z. l. nuttalli place their nest in shrubbery in distances from the ground ranging from 41-335 cm (Kern 1984, Blanchard 1941).
Z. l. nuttalli choose shrubs that are dense enough to provide effective concealment from above and below the nest (Chilton et al. 1995).
VEGETATION SURROUNDING THE NEST:
Adjacent to the nest is shrubbery that can include the same species as the nest site or any of the other coastal chaparral vegetation listed above used as a nest site. The surrounding vegetation must provide adequate concealment of the nest itself as the pair takes a circuitous route when coming and going from the nest (Chilton et al. 1995).
TYPICAL BREEDING DENSITIES:
Z. l. nuttalli range from 0.9 to 2.7 pairs/ha in California coastal scrub (Ralph and Pearson 1971).
Z. l. nuttalli are usually monogamous for the duration of the breeding season, often maintaining that pair bond throughout the winter. Petrinovich and Patterson (1982) found that about 25% of males and 50% of females have the same mate in the following breeding season. Divorce with both mates surviving into the next breeding season and each having new partners occurs in about 33% of Z. l. nuttalli pairs (Petrinovich and Patterson 1982). Polygamy is not uncommon with a male obtaining 2 mates; yet reproductive success of polygynously mated females is not greater than that of monogamously mated females (Petrinovich and Patterson 1978a).
Males are known to sing weakly and sporadically throughout the winter, but at some point in January, depending upon the weather, the male's singing becomes more vigorous and prolonged, accompanied by chasing and fighting of rival males to remove them from its territory. During this month females begin to trill and posture by fluttering their wings (Blanchard 1941). As early as 18 days prior to the first copulation that happens in early to late March, the male will sporadically chase his mate and jab her with his bill. About 3 weeks before coition he also directs towards his mate quiet singing interspersed during foraging each evening in the half-hour before dark. All this behavior intensifies and peaks just prior to and immediately following copulation (Chilton et al. 1995, Blanchard 1941). The female initiates copulation with a "Copulation-solicitation Display" in which she assumes a slight crouch, tail held nearly vertical, bill pointed upward, wings extended, quivering while trilling. She parts the feathers surrounding the cloaca and the male advances. His crown is raised while his bill is lowered and spread. He hops onto the female's back and maintains cloacal contact for 3 seconds before flying off (Blanchard 1941). Z. l. nuttalli have long courtships that can last up to 6-8 weeks because their reproductive organs at the beginning of courtship are not developed to their full size as they are during the breeding season. This is not applicable to the other migratory subspecies of Zonotrichia leucophrys (Chilton et al. 1995).
This varies from 2-5, with the most frequent clutch size being 3 (Chilton et al. 1995).
The female alone incubates the eggs (Chilton et al. 1995).
The female incubates for periods of 20 minutes at a time for the eggs to reach a set point temperature of 38 C whereupon she leaves the nest to rapidly forage for a time of usually 10 minutes or less before going back to incubate (Chilton et al. 1995). The male follows the female when she leaves the nest and does not stay behind to protect it. Hatching of eggs occurs on average 12.3 days from the start of continuous incubation (Chilton et al. 1995, Lewis 1975).
DEVELOPMENT AT HATCHING:
Young nestlings are hatched naked with little tufts of down along the feather tracts exposing transparent pink skin. They are quite helpless with their eyes closed and have the ability to only make feeble body movements. However, hatchlings are able to gape when the nest is jarred within 10 minutes of having hatched. The mean weight at hatching for Z. l. nuttalli is 2.4 g (Blanchard 1941, Banks 1959).
Within the first 3 days after hatching Z. l. nuttalli show primary feather eruption, their eyes begin to open and they can right their bodies if turned over. At 4 days nestlings cling to nest; at 5 days alarm calls are first heard and their eyes are fully open; and at 7 days they assume an upright position and crouch rather than gape when nest is disrupted. By day 8 they demonstrate wanting to escape from the nest, and at 10 days they have sufficient feather coverage for moderate thermoregulation and usually fledge by this day (Banks 1959)..
For the first few days after fledging, the juvenal Z. l. nuttalli stay within the bushes close to their nest and fly only short distances of 5-20m, if at all (Chilton et al. 1995). They are not entirely able to thermoregulate yet and most likely withstand prolonged periods of inactive nocturnal cold by becoming hypothermic (Chilton et al. 1995). At 16-17 days of age the juveniles begin to forage for themselves, while still begging and receiving food from their parents. During this period they also move to shrubs further away from the nest. By the time the juveniles are 37 days of age they may range 60 m from their natal territory. At 41 days they may range to 110 m, increasing that distance to around 270 m at 61 days. At this point they are well beyond their natal territory and will never to return to it again (Chilton et al. 1995).
Both parents continue to feed the young at the time of fledging. The male may take over the job of feeding them at about 16-17 days of age if the female begins work on a subsequent nest. The male will continue to feed until the young are about 30 days old and fairly independent, at which point he will begin to ignore them and even chase or fight with them (Lewis 1975, Blanchard 1941).
POST FLEDGING BIOLOGY OF OFFSPRING:
Immature Z. l. nuttalli having fledged will form loose flocks with others of the same subspecies and will remain in the near vicinity of their natal territory (Chilton et al. 1995).
POST BREEDING SOCIAL BEHAVIOR:
Adult pairs that remain together continue to inhabit their territory, patrolling and singing, albeit with far less fervor and jealousy, to the extent that flocks of immatures and even mateless adults can be included within their territory throughout the fall and winter (Blanchard 1941).
California's variable weather during winter and spring can fluctuate from one year to the next to such an extent, especially with regards primarily to mean temperatures, that there can be a discrepancy of as much as 41 days from the median date of first egg laid in first clutches for populations of Z. l. nuttalli. Generally however, egg laying begins in mid-March and is completed by late June (Chilton et al. 1995).
NUMBER OF BROODS:
The number of broods Z. l. nuttalli has depends upon the weather. During particularly wet winters it is not uncommon to have 4 clutches, but the more common amount is 2-3 (Chilton et al. 1995, Mewaldt and King 1977).
Brown-headed Cowbird (Molothrus ater) parasitism is on the rise for Z. l. nuttalli within urban areas such as San Francisco. This may lead possibly to a threat for their long-term survival if it were not for compensatory immigration to boost the population (Baptista 1972, Petrinovich and Patterson 1978b). Because Brown-headed Cowbirds prefer open exposed nests, Baptista suggests that Z. l. nuttalli in these urban spots are choosing sub-optimal nesting habitat that offers poor concealment (1972). Parasitized nests (67.2 cm, n=11) were located significantly higher than non-parasitized nests (39.0 cm, n=41) (Petrinovich and Patterson 1978b).
DISTURBANCE (natural or managed):
Z. l. nuttalli, seem to have their territories enhanced to a degree when human disturbance affects their natural habitat. The presence of roads or fences, for example, increases the amount of habitat patchiness, creating the matrix of grass, bare ground, and nearby shrubbery that these birds prefer most (Chilton et al. 1995). "Hybrid" habitats where fire or mechanical disturbances have increased diversity and the shrubs are young are also fitting territories for Z. l. nuttalli (Chilton et al. 1995). However, logging in coastal California may have lessened the barrier of unacceptable breeding habitat between Z. l. pugetensis and Z. l. nuttalli (Mewaldt et al. 1968), presenting a possible threat to the subspecies through genetic contamination.
ADJACENT LAND USE:
As long as suitable shrubbery or thickets are close, Z. l. nuttalli can easily incorporate cultivated farmland and other altered habitats into their territories. In a 1968 study, DeWolfe found pairs nesting and foraging in pastureland, using fence posts as perches from which to sing (Chilton et al. 1995).
Winter survival may be affected by the availability of food, water and cover (Chilton et al. 1995).
Predators contribute to 39% of egg and nestling mortality of Z. l. nuttalli nests in San Francisco (Petrinovich and Patterson 1983). The western terrestrial garter snake (Thamnophis elegans) is a primary predator of nestlings studied in San Francisco, but was not known to take eggs or mobile fledglings (Chilton et al. 1995). Other known predators include Common Barn Owl (Tyto alba), Sharp-shinned Hawk (Accipiter Striatus), and Crows (Corvus spp.). Scrub Jays (Aphelocoma coerulescens) take eggs, nestlings and fledglings, and American Kestrels (Falco sparverius) take adults and fledglings (Chilton et al. 1995).
DEMOGRAPHY AND POPULATION TRENDS:
AGE AND SEX RATIOS:
2.5 young/nest/yr, n = 186 pairs (Petrinovich and Patterson 1983).
Mean longevity of Z. l. nuttalli where n = 1,034 from egg is 6 mo, and from juvenile stage is 13 mo (Chilton et al. 1995 first breeding site is 110 m (n = 39, range = 0-586; Petrinovich and Patterson 1982). Winter range for female Z. l. nuttalli is 6 - 7 ha larger than for males, but the opposite is true in the summer where males tend to range more widely than the females (Chilton et al. 1995). Chilton et al. found a sustained population decline occurring (1995).
Ornamental exotic shrubs are used readily when native vegetation is lacking or does not provide an appropriate amount of concealment for a nest site (Chilton et al. 1995).
Z. l. pugetensis and Z. l. gambelii as well as Golden-crowned Sparrows (Z. atricapilla) are regularly found in mixed flocks during the winter with Z. l. nuttalli, and would benefit from having the same patchy combination of grass, bare ground and shrubs.
MONITORING METHODS AND RESEARCH NEEDS:
Although Nuttall's White-crowned Sparrows are a locally common and flexible species, research should be conducted to understand the effects of habitat quality on productivity and survivorship, particularly in urbanized and otherwise altered landscapes. Utilizing the MAPS (Monitoring Avian Productivity and Survival) protocol, color marking individuals, and conducting comprehensive nest success studies will allow biologists to understand differences in the demography of Nuttall's White-crowned Sparrows in areas with different habitat quality. The possibility and frequency of hybridization between Nuttall's White-crowned Sparrows and members of the pugetensis subspecies should be examined in order to understand the degree of genetic dilution occurring where the breeding ranges of these subspecies might begin to overlap due to anthropogenic factors.
ACTION PLAN SUMMARY
SPECIES: Nuttall's White-crowned Sparrow (Zonotrichia leucorphrys nuttalli)
Currently, Z. l. nuttalli does not have any state or federally listed conservation status.
HABITAT NEEDS and CONCERNS:
Z. l. nuttalli requires a patchy, fragmented habitat, which consists of grass (native or exotic), bare ground, and coastal scrub shrubbery. All 3 components are necessary and are most effective when they are integrated thoroughly with one another, allowing for foraging, safety, and a place to roost as well as to nest. Disturbance in the form of fire, logging, and farming has been beneficial to the extent that larger amounts of bare ground and grass have been incorporated into coastal scrub habitat allowing for a greater distribution of Z. l. nuttalli.
Disturbance that removes scrub vegetation to the point that suitable shrubs and thickets are removed from the needed combination of appropriate habitat, causes nests to be inadequately concealed and allows for possibly greater amounts of Brown-headed Cowbird parasitism to occur. The removal of nearby shrubs within a territory may also enable more attacks on foraging birds by predators such as Sharp-shinned Hawks.
Assess differences in demographics and population trends between Nuttall's White-crowned Sparrow populations in areas with various degrees of land alteration and urban encroachment, in order to understand the effects of anthropogenic activities such as brush clearing and residential development.
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Baptista, L. F. 1972. Cowbird parasitism on the White-crowned Sparrow and Wren-tit in the San Francisco Bay area. Auk 89: 879-882.
Blanchard, B. D. 1941. The White-crowned Sparrows (Zonotrichia leucophrys) of the Pacific seaboard: environment and annual cycle. Univ. Calif. Publ. Zool. 46: 1-178.
Chilton, G., M. C. Baker, C. D. Barrentine, and M. A. Cunningham 1995. White-crowned Sparrow. In A. Poole and F. Gill, eds. Birds North Amer. 183: 1 - 27
DeWolfe, B. B., and R. H. DeWolfe. 1962 Mountain White-crowned Sparrows in California. Condor 64: 378-389.
Kern, M.D. 1984. Racial differences in nests of White-crowned Sparrows. Condor 86: 455-466
Lewis, R. A. 1975. Reproductive biology of the White-crowned Sparrow (Zonotrichia leucophrys pugetensis Grinnell). I. Temporal organization of reproductive and related cycles. Condor 77: 46-59.
Mewaldt, L. R. 1964. Effects of bird removal on a winter population of sparrows. Bird Banding 35: 184-195.
Mewaldt, L. R., S. S. Kibby, and M. L. Morton. 1968. Comparative Biology of Pacific coastal White-crowned Sparrows. Condor 70: 14-30.
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Petrinovich, L., and T. L. Patterson. 1978a. Polygyny in the White-crowned Sparrow (Zonotrichia leucophrys). Condor 80: 99-100.
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Petrinovich, L., and T. L. Patterson. 1982. The White-crowned Sparrow: stability, recruitment, and the population structure in the Nuttall subspecies (1975-1980). Auk 99:1-14.
Petrinovich, L., and T. L. Patterson. 1983. The White-crowned Sparrow: reproductive success (1975-1980). Auk 100: ;811-825.
Ralph, C. J., and C. A. Pearson. 1971. Correlation of age, size of territory,
plumage, and breeding success in White-crowned Sparrows. Condor 73: 77-80.