Geographic Range
Ammodramus nelsoni
, or Nelson's sharp-tailed sparrows, have three separate distributions within the
Nearctic region. One population resides around Hudson Bay in Canada. The other two
inhabit both Canada and the United States: one population ranges along the north Atlantic
Coast from Quebec down to Maine and the other is in the center of North America, ranging
over Minnesota and northwest North Dakota to Alberta and southern Mackenzie River
basin in Canada. All populations migrate to winter along the southern Atlantic and
Gulf of Mexico coastlines. Small numbers are also found wintering in a similar habitat
along California’s coast.
Habitat
Ammodramus nelsoni
prefer grassy areas that are within wetlands. Common sites are freshwater marshes
at the edge of woodland lakes, brackish marshes, sedge bogs, and regions between creeks
and wet meadows. Willow trees are the preferred nesting site for this species, so
they are often found in habitats where these woody plants are abundant. Within these
habitats, a water depth between 1 to 10 inches is ideal. Water depths are most important
during the breeding season. If a site is too wet or too dry,
Ammodramus nelsoni
will most likely not live in that location.
Ammodramus nelsoni
winters in saltwater and brackish marshes.
- Habitat Regions
- temperate
- terrestrial
- Aquatic Biomes
- coastal
- brackish water
- Other Habitat Features
- estuarine
Physical Description
Ammodramus nelsoni
is noted for its sunny, golden-orange color extending from the eyebrows to the breast,
where it is mottled with darker stripes. The sparrow’s gray-striped crown is bordered
with dark brown, and the ear coverts are gray. The olive-brown upper body and neck
are notably streaked with white or gray. White extends down the abdomen to its brown,
tapered tail. They are small birds; weighing in at 19 to 21 g. They measure 11 to
13 cm in length and feature a 20 cm wingspan. The more common Le Conte’s sparrows
(
Ammodramus leconteii
) have a similar appearance to
Ammodramus nelsoni
. Differences include Le Conte’s sparrows' striped gray napes and more subtle sandy-streaked
backs.
Three subspecies exist, based on location. Two subspecies are found in the United
States and one inhabits British Columbia. Nelson's sharp-tailed sparrows are sexually
dimorphic. Both sexes look similar, but males are slightly larger than females. Juveniles
have brown ear coverts and less distinct facial markings.
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
- male larger
Reproduction
Male sexual behavior is a form of “scramble competition polygyny”. Males will actively
survey an area in search for females. Once a female is found, the male will intercept
them and attempt to copulate with the female, which is usually a forced mating. One
to several males may attempt to mate with a single female at one time, or several
males may mate with a single female one after the other in a short period of time.
This breeding method suggests that sperm competition is an important factor in this
species. Although mating is forced by the male, receptive females will perform a mating
invitation display during the time she is building a nest. She will crouch with her
tail and bill raised, wings folded and slightly raised, and make no vocalizations.
- Mating System
- polygynous
Ammodramus nelsoni
breeds annually during the spring and summer months. Females construct a cup-shaped
nest attached to low-lying reeds or willow branches. Location of the nest is critical
in habitats where water levels fluctuate, and females must select a height at which
nests will not be flooded. Clutches of three to seven eggs are laid in late spring
or early summer. The eggs hatch after about 11 days of incubation and 10 days later,
the young are able to leave the nest. The young receive continued care from the female
for an additional 20 days after fledging, when they become independent.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- oviparous
Females alone build the nest and incubate the eggs. Initially the female broods the
nestlings frequently after hatching and then less frequently after 4 to 5 days. Brooding
episodes may last up to 14 minutes, but usually are 2 to 6 minutes. Female Nelson's
sharp-tailed sparrows do not defend the nest if a predator is nearby. They fly off
the nest and stay quiet and hidden nearby. When the nestlings are in the fledgling
stage, females will give alarm calls to warn their offspring of predators.
There is very limited data on nestling feeding. It has been observed that young feed
almost exclusively on invertebrate prey. Food items are mostly found by the mother
in nearby vegetation, mud and water. The male has been observed to occasionally bring
food to the nest. Fledgelings remain near their mother who continues to care for
them for 20 days post-fledging.
- Parental Investment
- altricial
- female parental care
-
pre-fertilization
- provisioning
-
protecting
- female
-
pre-hatching/birth
-
provisioning
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
provisioning
-
pre-independence
-
provisioning
- female
-
provisioning
Lifespan/Longevity
Using banding data, the maximum observed lifespan is 10 years for males and 6 years
for females.
Estimates of minimum annual survival of adults in 2 cohorts (in New York) were 60.3%
and 54.7% in males, and 63.3% and 53.0% in females. Offspring survival into first
fall is estimated as 31.1%. In a 2-year study in Rhode Island, tidal flooding caused
60% of egg and nestling mortality. Flooding was also found to be the main cause of
egg and nestling mortality in Canada and New York. There is little known regarding
causes of adult mortality.
Behavior
Ammodramus nelsoni
spends most of its time foraging, except during breeding season when males spend
large amounts of time singing and searching for females. Foraging birds will run in
short spurts, walk, or hop while searching for insects.
Ammodramus nelsoni
will often run and stop, climb vegetation and survey the area when not foraging.
When alarmed, these sparrows will run crouched down with their heads lowered. Most
flights are relatively short and local, and their characteristics vary depending on
social context, associated behavior, or destination.
Observed meetings between males is usually only when one male actively forces another
male off a perch or one male retreats as another approaches. Dominance between males
during breeding season has yet to be better understood. A singing male may cease singing
when another male approaches or sings nearby, but counter-singing has not been observed.
There is a loose dominance hierarchy apparent within different subspecies of
Ammodramus nelsoni
. In New York, females have been observed fighting with males or chasing them off
when the male tries to force the female into mating. Females will often chase males
out of the immediate nesting area. They will use threatening calls or displays to
ward off males. In New Brunswick, females have been observed to be more passive towards
males.
Ammodramus nelsoni
is a migratory species that brees in select regions of the northeast half of the
United States and near the Hudson Bay in Canada. In fall, this species flies south
to marsh habitats across the Gulf Coast or the southern Atlantic coast of the United
States. During migration,
Ammodramus nelsoni
is often observed feeding in groups of 10 to 40 individuals, but at optimal locations
they may amass in groups of up to 100.
Home Range
Males are non-territorial. They typically concentrate their daily activities in large
overlapping home ranges. Flight paths of males will cross and perching sites are often
shared by several males. Male home ranges are estimated to be between 1.2 to 1.6 ha
in New Jersey and 3.0 to 5.7 ha in New York. The home range size for males in Canada
is unknown, but believed to be much larger than the southern populations.
Communication and Perception
Males use songs to attract females, but unlike many songbirds they do not use this
song to establish territory. They often sing in flight. Their most common song can
be mnemonically described as 'k-chinnnng doot' and sounds like two short chips with
a dry hiss in between. Females use warning calls to alert offspring of danger and
threatening calls to ward off males from nests. No observations of female songs have
been made. Females also use body posture to communicate willingness to mate. When
a female encounters a male and is ready to breed, she may crouch with her tail and
bill raised, and hold her wings folded and slightly raised. Like most birds,
Ammodramus nelsoni
perceives its environment through visual, auditory, chemical, and tactile stimuli.
- Communication Channels
- acoustic
Food Habits
Ammodramus nelsoni
is an omnivore, and procures the bulk of its food from grass stems or on the ground.
In warmer months, their diets include insects, spiders, amphipods, and other small
invertebrates. During winter months, seeds and grains provide the sparrows' sustenance.
- Primary Diet
- omnivore
- Animal Foods
- insects
- terrestrial non-insect arthropods
- Plant Foods
- seeds, grains, and nuts
Predation
Females silently abandon their nests and hide when a potential ground predator comes
near. She will give warning calls when dependent young are present and fly within
10 to 15 m of nest. Females return to the nest after the potential predator leaves
the immediate nest area. An alarm call may be given when an aerial predator approaches,
but typically the sparrows silently find cover. No nest-distraction displays have
been recorded. Like most sparrows, their plumage features stripes in shades of brown,
gray, and black that blend in well with their grassy environments. Known predators
on adults and nests include
northern harriers
,
short-eared owls
,
fish crows
,
Norway rats
, and
garter snakes
. Though not confirmed, suspected predators include
herons
,
egrets
,
glossy ibises
,
American crows
, and
black snakes
.
- Anti-predator Adaptations
- cryptic
Ecosystem Roles
As omnivores, these sparrows likely affect local seed distribution as well as insect
populations. The adults and young also serve as food for several aerial and land
predators. Nest parasitism sometimes occurs in
Ammodramus nelsoni
nests. The only documented brood parasites for this species are brown-headed cowbirds
(
Molothrus ater
).
- brown-headed cowbirds ( Molothrus ater )
Economic Importance for Humans: Positive
Nelson's sharp-tailed sparrows do not have any economic benefits for humans.
Economic Importance for Humans: Negative
There are no known negative effects of Nelson's sharp-tailed sparrows on humans.
Conservation Status
The main threat to
Ammodramus nelsoni
is habitat loss due to human destruction; mostly because of conversion of grassland
and marshes for agricultural uses. Because specific water depth is important to the
species, it is essential to protect large areas of habitat to make certain that the
ideal water conditions are present in at least a few areas within a wetland. Currently,
the International Union for Conservation of Nature and Natural Resources lists this
species as Least Concern and considers the population to be stable and widespread.
However, increasing human development and resulting habitat loss should be monitored
closely. As a migratory species,
Ammodramus nelsoni
is protected under the United States Migratory Bird Act.
Additional Links
Contributors
Beth Twaddle (author), Minnesota State University, Mankato, Robert Sorensen (editor), Minnesota State University, Mankato, Rachelle Sterling (editor), Special Projects, Catherine Kent (editor), Special Projects.
- Nearctic
-
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- temperate
-
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
- terrestrial
-
Living on the ground.
- coastal
-
the nearshore aquatic habitats near a coast, or shoreline.
- brackish water
-
areas with salty water, usually in coastal marshes and estuaries.
- marsh
-
marshes are wetland areas often dominated by grasses and reeds.
- bog
-
a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.
- estuarine
-
an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.
- endothermic
-
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- polygynous
-
having more than one female as a mate at one time
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- altricial
-
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
- female parental care
-
parental care is carried out by females
- arboreal
-
Referring to an animal that lives in trees; tree-climbing.
- motile
-
having the capacity to move from one place to another.
- migratory
-
makes seasonal movements between breeding and wintering grounds
- solitary
-
lives alone
- acoustic
-
uses sound to communicate
- cryptic
-
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
- omnivore
-
an animal that mainly eats all kinds of things, including plants and animals
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
References
Cooper, J., S. Beauchesne. 2004. "Nelson's Sharp-tailed sparrow" (On-line). British Columbian Government. Accessed May 01, 2011 at http://www.env.gov.bc.ca/wld/frpa/iwms/documents/Birds/b_nelsonssharptailedsparrow.pdf .
Greenlaw, J., J. Rising. 1994. Saltmarsh Sparrow (Ammodramus caudacutus). The Birds of North America Online , 112: Online. Accessed May 03, 2011 at http://bna.birds.cornell.edu/bna/species/112 doi:10.2173/bna.112 .
Shriver, W., T. Hodgman, . Hanson. 2011. Nelson's Sparrow. The Birds of North America (Online) , 719: Online. Accessed May 03, 2011 at http://bna.birds.cornell.edu/bna/species/719/articles .
Woolfenden, G. 2007. Wintering Distributions and Migration of Saltmarsh and Nelson's Sharp-Tailed Sparrows. The Wilson Journal of Ornithology , 119: 361- 377. Accessed April 27, 2011 at http://www.jstor.org/stable/20456021 .
MN DNR. 2011. "Ammodramus nelsoni" (On-line). Minnesota Department of Natural Resources. Accessed April 27, 2011 at http://www.dnr.state.mn.us .
BirdLife International. 2009. "IUCN Red List of Threatened Species: Ammodramus nelsoni" (On-line). International Union for Conservation of Nature and Natural Resources. Accessed May 18, 2011 at http://www.iucnredlist.org/apps/redlist/details/150504/0 .
Montana Natural Heritage Program and Montana Fish, Wildlife and Parks. 2011. "Nelson's Sparrow — Ammodramus nelsoni" (On-line). Montana Field Guide. Accessed May 01, 2011 at http://fieldguide.mt.gov/detail_ABPBXA0070.aspx .