Animal Diversity Web

Geographic Range

Pine siskins (Carduelis pinus) are found across the entirety of the Nearctic, with the exception of Greenland and northern continental North America. They can be found as far north as southern Alaska and as far south as Guatemala. They span as far west as Kodiak Island, Alaska across North America to their easternmost points of Newfoundland and Labrador, Canada. Their southernmost range includes western Guatemala to the Mexican Isthmus. Individual pine siskins migrate seasonally but do not reliably migrate back to the same breeding locations each year. Rather, they follow food resources across their wide geographic range. Breeding is restricted to the northernmost region of the pine siskins' range. This includes southern Alaska, eastward across Canada to the eastern edge of Newfoundland and Labrador. In the non-breeding season, siskins range throughout the continental United States, Canada (the southern tip of Alberta, Saskatchewan, and Manitoba), and Mexico. Pine siskins can be found year-round in the western United States, southern Canada (from British Columbia to the territory of St. Pierre and Miquelon), western Mexico, and central Guatemala. Pine siskins can be found year-round in the western United States, southern Canada (from British Columbia to the territory of St. Pierre and Miquelon), western Mexico, and central Guatemala. (Arnaiz-Villena, et al., 2012; BirdLife International, 2016)

• Biogeographic Regions
• nearctic
  • native

Habitat

Pine siskins live in coniferous or mixed coniferous-deciduous forests. Coniferous forests are made up of evergreen trees, which are primarily pine (Pinus), spruce (Picea), fir (Abies), and larch (Larix) trees that bear needles and cones. These temperate forests experience moderate levels of yearly precipitation. The forest floor is rich in nutrients from old tree and plant remains that promote moss and fungi growth. In a deciduous forest trees including oak (Quercus), beech (Fagus), birch (Betula), elm (Ulmus), maple (Acer), and linden (Tilia) tree. Deciduous forests experience all four seasons moderately and rely on year-round precipitation. Pine siskins live in coniferous or coniferous-deciduous habitats because they eat the seeds of coniferous trees and rely on the year-round protections of these trees and shrubs.

During the breeding season, siskins move to the outer edges of coniferous forests. In the summer, siskins can be found in brush on the edges of the forest because they eat the insects from nearby grasses and bushes. In fall and winter, the siskins leave the forest to seek food in open fields from herbaceous sources. Then they return to the forests to find shelter in the conifers and deciduous trees.

Siskins also inhabit suburban neighborhoods with sufficient trees for shelter. Suburban neighborhoods are a consistent food source for many birds due to the frequency of bird feeders in these neighborhood settings. (BirdLife International, 2016; Hill and McGraw, 2004; Hutto, et al., 1986; Nguembock, et al., 2009)

• Habitat Regions
• temperate

• Terrestrial Biomes
• savanna or grassland
• forest

• Other Habitat Features
• suburban
• agricultural

Physical Description

Pine siskins are songbirds ranging from 11 centimeters to 14 centimeters long, 12 grams to 18 grams in mass, and with wingspaces of 18 centimeters to 22 centimeters. Like most finches, siskins have moderately colorful plumage and sharp, triangular beaks specific for seed-eating from cones. Their breast is white and streaked with brown feathers. Their head plumage is made of smaller feathers with a more concentrated brown coloration. From their nape to rump, siskins display a similarly streaked pattern – dark brown tones intermixed with light brown and white feathers. Their feathers increase in length moving from anterior to posterior, which creates greater spaces in the distinct feather coloration moving from the head to the tail of the siskin.

While in flight or during mating events, siskins display bright yellow markings on their pointed wings and forked tails. Their wing feathers are brown, edged with white. A yellow band is present through the mid-wing when their wings are spread. This yellow line is indicative of hierarchical rank amongst siskins. When perched, yellow coloration is intermixed throughout the tucked wings, giving yellow markings on the left and right sides of the bird. Their tail feathers display bright yellow until mid tail where the feathers transitions to dark brown feathers edged in white. Their short pointed beak can range from brown to black and their legs and eyes are dark drown. This is not a sexually dimorphic species and juveniles present with similar markings as adults. Juveniles have pink beaks and buffy-yellow and light brown plumage until they have matured into their adult appearance by fall of their first year. Siskin eggs are 1.5 to 1.9 centimeters in length and 1.1 to 1.4 centimeters in width but there are no recordings of juvenile size post hatching. (BirdLife International, 2016; Humber, et al., 2009; Jardine, 2014; McCabe and McCabe, 1928; Yunick, 1976)

• Other Physical Features
• endothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes alike

• Range mass

  12 to 18 g

  0.42 to 0.63 oz

• Range length

  11 to 14 cm

  4.33 to 5.51 in

• Range wingspan

  18 to 22 cm

  7.09 to 8.66 in

Reproduction

Pine siskins become sexually mature within their first year and females reproduce twice per breeding season. The siskin breeding season is flexible depending on food supply. They can breed from early spring through late summer. Siskins can breed in cold temperatures, which makes food their determining factor.

Prior to breeding, male siskins preform a courtship display by circling the canopy and singing a mating song that lasts about 13 seconds with various “zweeeee” sounds. The males continue to sing their mating song while showing off their bright yellow tail and wing markings until female siskins begin to “coo” back with a soft low-pitched call. Females mate with males that have an experienced song and offer food during copulation. During the breeding season, female siskins are polyandrous and breed with an average of two males. This breeding can occur once during each of two breeding cycles of the season or intermixed throughout the breeding period. Once the female has chosen a male, copulation is finalized and a pair bond forms. (BirdLife International, 2016; Johnson, et al., 1993; Perry, 1965)

• Mating System
• polyandrous

After a pair bond forms, the female makes the nest and the male continues to sing and return with food. The nest is built between 3 and 12 meters off above the forest floor, located mid-branch of a coniferous or deciduous tree to ensure protection from predators. Though 3-4 eggs per nest is typical for siskins, females can produce 2-5 eggs per clutch. Female siskins incubate the eggs for 13 days while the male seeks food for his mating partner. Juvenile siskins weigh between 1 gram and 2.5 grams when the hatch (average 1.5 g). They remain in the nest for an average of 15 days before they fledge. Three weeks post-hatching.the juveniles can feed on their own and reach independence. Within their first year, the juveniles reach sexual maturity and can breed during the next spring breeding cycle. (Arnaiz-Villena, et al., 2012; BirdLife International, 2016; Johnson, et al., 1993; Luttrell, et al., 2001; Perry, 1965; Yamadaa and Bouldingb, 1998)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• oviparous

• Breeding interval

  Once or twice a year

• Breeding season

  March-August

• Range eggs per season

  2 to 5

• Average time to hatching

  13 days

• Average fledging age

  15 days

• Average time to independence

  21 days

• Average age at sexual or reproductive maturity (female)

  1 years

• Average age at sexual or reproductive maturity (male)

  1 years

Male siskins invest in pre-breeding behaviors. Males expend energy during their courtship display as they sing and fly in circle above the females. They continue to expend energy resources during the breeding period and incubation time as they find food for the female. During the courtship and breeding period, the female builds the nest and then proceeds to lay and incubate the eggs and the male is feedig his mate every 30-60 minutes. The nest is composed of twigs, bark, roots, moss, fur, feathers, and other small semi-flexible objects and takes the female 5 to 6 days to construct. In suburban areas, the female uses other debris including, paper, string, cloth and cotton. Soft material lines the inside of the nest so as not to disrupt the eggshell. The external diameter of the nest is 10 centimeters on average and the internal diameter is 5 centimeters, with a nest height of 4 centimeters. Females build nests to be able to spread her wings and shield the juveniles from rain or bright sun during the 13-17 post-hatch days.

Once hatched, male siskins feed the females and then females feed the chicks via regurgitation. The males feed the female for 8 days after the eggs hatch and the majority of feeding takes place in the morning. (BirdLife International, 2016; Nguembock, et al., 2009; Perry, 1965)

• Parental Investment
• female parental care
• pre-hatching/birth
  • provisioning
    • male
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • male
  • protecting
    • female
• pre-independence
  • provisioning
    • male
  • protecting
    • female

Lifespan/Longevity

Pine siskins live an average of 9 years in the wild. No other data are available regarding the lifespan of the pine siskin, and they are not kept in captivity. (BirdLife International, 2016)

• Average lifespan
  Status: wild

  9 years

Behavior

Feeding behavior is very important for male-male, female-female, and male-female siskin relationships. Partnership feeding occurs year round in the siskin population. This feeding is most frequent during breeding season when males bring food to the females, but beak-to-beak feeding interaction occurs between same sex and heterosexual pairs after the breeding season ends.

Siskins are aggressive towards other species during breeding season and occasionally during throughout winter months. They antagonize many species including evening grosbeaks (Hesperiphona vespertina), red crossbills (Loxia curvirostra), and white-winged crossbills (Loxia leucoptera). When competition reduces after breeding season, siskins associate with American goldfinches (Spinus tristis), redpolls (Acanthis) and crossbills (Loxia). Body movement is indicative of the behavior that siskins display. Siskins are strong fliers and can escape competition quickly. Siskins are good at starting fights, as they can outmaneuver their competition. To leave the ground, they beat the air rapidly with their wings and take flight. Once airborne, they move their wings in a wave shape to maintain altitude. In confined spaces like dense canopies, they walk and hop across tree branches. Siskins will lunge when they feel threatened by a nearby species and depending on the surrounding forest density, they will fight from 3-4 meters in the air.

Siskins are an arboreal species that defend their nesting territory in the mid-range branch region of conifer trees and stack their nests in loose colonies. Before breeding occurs, the male circle above the canopy and sing to nearby females. Once a pair has formed, the male will continue to preform via song and flight, while the female builds the nest. The male will feed the female he is pursuing and continue to feed her throughout the duration of the egg incubation period. Once hatched, the juveniles are fed via regurgitation from the mother that was provided food from the male siskin. The male feeds the female for 8 days after the eggs hatch and the majority of feeding takes place in the morning. In between feeding events for the young, the mother will clean the fecal matter out of the nest by swallowing the nestlings excrement for 5-6 days after the young hatch. When sleeping, siskins tuck their heads between their shoulders to reduce surface area and conserve heat.

Siskins migrate in large groups, moving farther south when food resources become limited in their Northern location. Siskins do not follow the same migratory pattern each year, but instead navigate as a group to locations with the most abundant food opportunities. These locations range across continental America, along the lower portion of Canada, and Mexico. Siskins groups spread out once a new location is chosen. While they form small territories within the new area, siskins continue to interact with their flock by visiting other siskins’ nests. (BirdLife International, 2016; Hill and McGraw, 2004)

• Key Behaviors
• arboreal
• flies
• diurnal
• motile
• migratory
• territorial
• social

• Range territory size

  0.9 to 2.3 m^2

Home Range

Pine siskins defend an area around their nest, about 0.6 to 1.7 meters in diameter, during the breeding season. This equates to about 0.9-2.3 square meters. (BirdLife International, 2016)

Communication and Perception

Male pine siskins rely on both their plumage and song to find a mate. Young males learn to sing long, complex melodies within their first year of life. Their mating songs last about 13 seconds and are used to gain the attention of a potential female. The males make sharp, high pitched, elongated “zweeeee” sounds when singing to the females. During feeding and flight, they use a wheezy “zreeeet” sound. Siskins make a short “zwee” sound during flight, as they call with each flap of their wings. When calls are not being used for mating purposes, the songs are quick and more aggressive. Females use a lower pitched husky call to males that can sustain over longer distances.

Pine siskins use their vision to increase scanning observations every second when they are feeding alone, as compared to feeding with one or more other siskins. Female siskins use vision to choose their mate. Unlike other bird species, female siskins distinctly choose a male with less exaggerated coloration. The females pick natural colors and less defined yellow markings on the male siskins.

These siskins fight when territorial, so tactile efforts are made. (BirdLife International, 2016; Luttrell, et al., 2001; Ortega-Álvarez and MacGregor-Fors, 2009; Toland, 1985)

• Communication Channels
• visual
• tactile
• acoustic

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

Pine siskins are granivores, meaning their diet primarily consists of seeds. They use their pointed beaks to break open cones and extract seeds from coniferous trees. Siskins live in coniferous-deciduous forests because they eat the seeds of pine (Pinus), spruce (Picea), redcedar (Juniperus), and hemlock (Tsuga) trees. They will also eat seeds from a variety of weeds, such as chickweed (Strellaria media), ragweed (Ambrosia), and dandelions (Taraxacum). Siskins also feed on sunflower (Helianthus) seeds, which are used as bait in siskin studies to monitor behavior and feeding patterns. Balph and Balph (1979) noticed that siskins had acquired a unique feeding adaptation to help them overcome the tough outer shell of the sunflower seed. They observed siskins waiting for evening grosbeaks (Hesperiphona vespertina) to open the sunflower seeds and then the siskins would swoop in and eat the remaining seeds and seed fragments from the ground. Siskins will continue to feed this way until the grosbeaks become aggressive and then the siskins will return to eating seeds that they can husk independently. Pine siskins have also adapted to using bird feeders in suburban communities.

In the summer months, siskins will also consume insects as another food source. Over 2,000 spruce budworm (Choristoneura fumiferana) eggs were found in the stomach of a siskin during a study by Jennings and Crawford (reported in Dawson, 2014). Siskins use larvae and insects to feed to their young during the summer months when insects are more abundant. Siskins also eat road salt and sap from maple (Acer) trees. While siskins have multiple food sources, they are quick to alter their migratory patterns based on food source sustainability. Their breeding timeline is also flexible due to food availability. (Balph and Balph, 1979; Benkman and Lindholm, 1991; Dawson, 2014; Humber, et al., 2009)

• Primary Diet
• herbivore
  • granivore

• Animal Foods
• insects

• Plant Foods
• seeds, grains, and nuts
• flowers
• sap or other plant fluids

Predation

Pine siskins are found in suburban areas with sufficient conifer canopy coverage because they have learned how to feed from bird feeder with small seeds. This food source provides an opportunity for domestic cats (Felis catus) to prey on siskins. Less common predators include the eastern red squirrels (Tamiasciurus hudsonicus), sharp-shinned hawks (Accipiter striatus), Cooper’s hawks (Accipiter cooperii), northern shrikes (Lanius excubitor), blue jays (Cyanocitta cristata), and American crows (Corvus brachyrhynchos). Brown-headed cowbirds (Molothrus ater) are amongst the most detrimental predators of the siskin. Female cowbirds lay their eggs in siskins' nests and fly away to a nearby tree to observe their egg’s surrogate nest. The mother cowbird will destroy the siskin nest if the siskin mother does not care for the cowbird egg. To avoid losing her nest, the female siskin will incubate the cowbird egg. (Astheimer, et al., 1991; BirdLife International, 2016; Hutto, et al., 1986; Jardine, 2014)

• Known Predators

  • domestic cats (Felis catus)
  • eastern red squirrels (Tamiasciurus hudsonicus)
  • sharp-shinned hawks (Accipiter striatus)
  • Cooper’s hawks (Accipiter cooperii)
  • northern shrikes (Lanius excubitor)
  • blue jays (Cyanocitta cristata)
  • American crows (Corvus brachyrhynchos)
  • brown-headed cowbirds (Molothrus ater)

Ecosystem Roles

Pine siskins build nests in and inhabit the same geographical range as the brown-headed cowbirds (Molothrus ater). The cowbird does not build a nest or take care of its own young, but rather lays their eggs in siskins nests. Female siskins must incubate and care for the cowbirds eggs, which ultimately kills the female and juvenile siskins because they cannot compete with the feeding demands of a juvenile cowbird.

Pine siskins in Maryland, Oregon, Washington, British Columbia and Virginia are prone to carry bacteria salmonella (Salmonella typhimurium). They can also be carriers of the western blacklegged tick (Ixodes pacificus) that spreads Lyme disease spirochete (Borrelia burgdorferi). Other parasites infecting siskins include protozoans (Haemoproteus fringillae/orizovora, Haemoproteus, Leucocytozoon fringillarum, Leucocytozoon, and Trypanosoma avium). Feather mites include Proctophyllodes spini and rabbit ticks include Haemaphysalis leporispalustris. (Hill, 1976; Locke, et al., 1973; Nicholls and Callister, 1996)

Economic Importance for Humans: Positive

Humans benefit from pine siskins because of ecotourism (bird watching) and because siskins consume forest insects. (BirdLife International, 2016)

• Positive Impacts
• ecotourism

Economic Importance for Humans: Negative

Pine siskins may carry salmonella (Salmonella typhimurium). They can also be carriers of the western blacklegged tick (Ixodes pacificus) that spreads Lyme disease spirochete (Borrelia burgdorferi). these bacterial infections could be transferred to humans. (Dawson, 2014)

• Negative Impacts
• injures humans
  • carries human disease

Conservation Status

The IUCN Red List notes pine siskins to be of “Least Concern.” Siskins are protected under the US Migratory Bird Act. The US Federal List, State of Michigan List, and CITES offer no special status regarding pine siskins.

Many threats exist for these birds. Human interference may cause these birds to desert their nests and cause nest failure. Salt on winter roads could attract siskins to high-traffic areas. Dawson (2014) summarizes a few cases in which chemicals have killed siskins: in Idaho, the pesticide disulfotan killed birds, while gold-mining efforts and cyanide waste killed birds in South Dakota. Salmonella infections also could be spread by congregations at bird feeders.

Indirect management strategies to maintain pine siskin populations include minimizing large-scale clearcuts and creating more parks with coniferous trees. (BirdLife International, 2016; Dawson, 2014)

• IUCN Red List

  Least Concern

• US Migratory Bird Act

  Protected

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Contributors

Taylor Hawkins (author), Radford University, Alex Atwood (editor), Radford University, Layne DiBuono (editor), Radford University, Lindsey Lee (editor), Radford University, Karen Powers (editor), Radford University, Joshua Turner (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Arnaiz-Villena, A., C. Areces, D. Rey, M. Enriquez-de-Salamanca, J. Alonso-Rubio, V. Ruiz-del-Valle. 2012. Three different North American siskin/goldfinch evolutionary radiations (genus Carduelis): Pine siskin green morphs and European siskins in America. The Open Ornithology Journal, 5/1: 73-81.

Astheimer, L., W. Buttemer, J. Wingfield. 1991. Interactions of corticosterone with feeding, activity and metabolism in passerine birds. Scandinavian Journal of Ornithology, 23/3: 355-365.

Balph, D., M. Balph. 1979. Behavioral flexibility siskins in mixed species foraging groups. The Condor, Condor 81: 211-212.

Benkman, C., A. Lindholm. 1991. The advantages and evolution of a morphological novelty. Nature, 349: 519-520.

Bennetts, R., R. Hutto. 1985. Attraction of social fringillids to mineral salts: An experimental study. Journal of Field Ornithology, 56/2: 187-189.

BirdLife International, 2016. "Spinus pinus" (On-line). The IUCN Red List of Threatened Species 2016: e.T22720359A94666039. Accessed January 23, 2018 at http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22720359A94666039.en.

Dawson, W. 2014. "Pine siskin Spinus pinus" (On-line). version 2.0. In The Birds of North America (A. F. Poole, Editor). Accessed January 25, 2018 at https://doi.org/10.2173/bna.280.

Hill, G., K. McGraw. 2004. Correlated changes in male plumage coloration and female mate choice in cardueline finches. Animal Behaviour, 67/1: 27-35.

Hill, R. 1976. Host-parasite relationships of the brown-headed cowbird in a prairie habitat of west-central Kansas. The Wilson Bulletin, 88/4: 555-565.

Humber, J., D. Brodbeck, I. Warkentin. 2009. Use of spatial and colour cues by foraging pine siskins (Carduelis pinus): A field study. Behavioural Processes, 80/3: 233-237.

Hutto, R., S. Pletschet, P. Hendricks. 1986. A fixed-radius point count method for nonbreeding and breeding season use. The Auk, 103/3: 593-602.

Jardine, D. 2014. On the spring-squall arrival of a pine siskin (Carduelis pinus). Counterpoints, 452: 27-37.

Johnson, K., D. Rosetta, D. Burley. 1993. Preferences of female American goldfinches (Carduelis tristis) for natural and artificial male traits. Behavioral Ecology, 4/2: 138–143.

Koenig, W., J. Knops. 2001. Seed-crop size and eruptions of North American boreal seed-eating birds. Journal of Animal Ecology, 70/4: 609–620.

Locke, L., R. Shillinger, T. JareedTeresa. 1973. Salmonellosis in passerine birds in Maryland and West Virginia. Journal of Wildlife Diseases, 9/2: 144-145.

Luttrell, M., D. Stallknecht, S. Kleven, D. Kavanaugh, J. Corn, J. Fischer. 2001. Mycoplasma gallisepticum in house finches (Carpodacus mexicanus) and other wild birds associated with poultry production facilities. Avian Diseases, 45/2: 321-329.

MacDougall-Shackleton, S., M. Katti, T. Hahn. 2006. Tests of absolute photorefractoriness in four species of cardueline finch that differ in reproductive schedule. Journal of Experimental Biology, 209/19: 3786-3794.

McCabe, T., E. McCabe. 1928. The plumage of the pine siskin. The Condor, 20/4: 221-227.

Nguembock, B., J. Fjeldså, A. Couloux, E. Pasquet. 2009. Molecular phylogeny of Carduelinae (Aves, Passeriformes, Fringillidae) proves polyphyletic origin of the genera Serinus and Carduelis and suggests redefined generic limits. Molecular Phylogenetics and Evolution, 51/2: 169-181.

Nicholls, T., S. Callister. 1996. Lyme disease spirochetes in ticks collected from birds in midwestern United States. Journal of Medical Entomology, 33/3: 379-384.

Ortega-Álvarez, R., I. MacGregor-Fors. 2009. Living in the big city: Effects of urban land-use on bird community structure, diversity, and composition. Landscape and Urban Planning, 90/3-4: 189-195.

Perry, A. 1965. The nesting of the pine siskin in Nebraska. The Wilson Bulletin, 77/3: 243-250.

Toland, B. 1985. Food habits and hunting success of Cooper's hawks in Missouri. Journal of Field Ornithology, 56/4: 419-422.

Yamadaa, S., E. Bouldingb. 1998. Claw morphology, prey size selection and foraging efficiency in generalist and specialist shell-breaking crabs. Journal of Experimental Marine Biology and Ecology, 220/2: 191-211.

Yunick, R. 1976. Delayed molt in the pine siskin. Bird-Banding, 47/4: 306-309.