Demography and Populations

The Northern Flicker has a relatively "fast" life history compared to most other woodpeckers and other avian species of similar body size (249 Fisher, R. J., and K. L. Wiebe (2006). Effects of sex and age on survival of Northern Flickers: A six-year field study. Condor 108(1):193–200. Close , 250 Wiebe, K. L. (2006). A review of adult survival rates in woodpeckers. Annales Zoologici Fennici 43(2):112–117. Close ). As detailed below, this entails breeding in the first year of life, large clutches, and relatively short lifespan. The breeding population for the United States and Canada is estimated at 11,000,000 individuals, and the global population is estimated at 12,000,000 (251 Partners in Flight (2020). Population Estimates Database, version 3.1. Close ).

Age at First Breeding

Both sexes can breed when they are about 1 year of age (Formative Plumage), and it seems that most attempt to do so. Of 1,675 breeding attempts recorded at Riske Creek in central British Columbia over a timespan of 18 years, 39% involved a yearling female and 37% a yearling male (252 Wiebe, K. L. (2018). Age-related improvements in fecundity are driven by the male in a bird with partially reversed sex roles in parental care. Oecologia 188:1095–1104. Close ,249 Fisher, R. J., and K. L. Wiebe (2006). Effects of sex and age on survival of Northern Flickers: A six-year field study. Condor 108(1):193–200. Close ).

Intervals Between Breeding

Mark-recapture analysis suggests that the Northern Flicker breeds annually (249 Fisher, R. J., and K. L. Wiebe (2006). Effects of sex and age on survival of Northern Flickers: A six-year field study. Condor 108(1):193–200. Close ).

Clutch Size and Number of Clutches per Season

The Northern Flickeris among those species of woodpeckers in which clutch size increases with latitude (253 Koenig, W. D. (1986). Geographical ecology of clutch size variation in North American woodpeckers. Condor 88(4):499–504. Close ). Various estimates for clutch sizes at different geographical locations are in Eggs. At Riske Creek, the size of first clutches: 7.99 ± 1.3 SD (n = 1,579) and for second (replacement) clutches: 6.83 ± 1.1 SD (n = 266); for all clutches pooled: 7.81 ± 1.4 SD (range 2‒13, n = 1,872) (KLW) . Only one clutch (brood) is reared but a female may replace clutches that are destroyed if there is still enough time in the breeding season to rear offspring. The probability of renesting according to date for females at Riske Creek is plotted in (254 Wiebe, K. L. (2003). Delayed timing as a strategy to avoid nest-site competition: testing a model using data from starlings and flickers. Oikos 100(2):291–298. Close ). Up to 2 replacement clutches for a female have been observed at Riske Creek. Clutch size declines significantly with laying date even within first clutches. The number of eggs fell by 0.056 eggs/day for yearling females and by 0.062 eggs/day for older females (254 Wiebe, K. L. (2003). Delayed timing as a strategy to avoid nest-site competition: testing a model using data from starlings and flickers. Oikos 100(2):291–298. Close ).

Clutch size also varies with the age of parents. As a female aged, clutch size increased from the first year of life (yearling females lay about 7.5 eggs) to the second year (about 8.5 eggs) but did not change significantly thereafter whereas clutch size increased with the age of the male partner, up to age 5 (252 Wiebe, K. L. (2018). Age-related improvements in fecundity are driven by the male in a bird with partially reversed sex roles in parental care. Oecologia 188:1095–1104. Close ). Thus, females seem to adjust the number of offspring according to the quality and parental effort of the male.

Annual and Lifetime Reproductive Success

At Riske Creek, 71% of 1023 nests survived to the hatching stage. The other nests were either depredated (16%), evicted by European Starling (Sturnus vulgaris) (5.4%), or the nest tree blew down (0.6%). A handful of nests were abandoned for unknown cause (see 254 Wiebe, K. L. (2003). Delayed timing as a strategy to avoid nest-site competition: testing a model using data from starlings and flickers. Oikos 100(2):291–298. Close , 206 Fisher, R. J., and K. L. Wiebe (2006). Nest site attributes and temporal patterns of northern flicker nest loss: effects of predation and competition. Oecologia 147(4):744–753. Close ), possibly attributable to a predation attempt or a result of competition with other species for the nest cavity. Of 1494 nests which survived to the hatchling stage at Riske Creek, 89.8% fledged at least one offspring, or when the sample of all nesting attempts is considered (n = 2,072), 69.9% of initiated nesting attempts produced at least one fledgling.

On the central plains in the United States, 78% of nests (n = 119) survived to the hatching stage, and of those nests with hatchlings, 86% of nests survived to age of nestling banding, 11–14 d after hatching (WSM). In Wisconsin, 4 of 12 nests were depredated (171 Duncan, S. (1990). Auditory communication in breeding Northern Flickers (Colaptes auratus). Ph.D. dissertation, University of Wisconsin, Milwaukee, WI, USA. Close ), and on Nantucket Island, Massachusetts, 8 of 30 nests failed generating an overall success rate of 73% (222 Dennis, J. V. (1969). The Yellow-shafted Flicker (Colaptes auratus) on Nantucket Island, Massachusetts. Bird-Banding 40:290–308. Close ). In salvage-logged sites in Idaho, average nest success was about 64% (n = 293) (255 Saab, V. A., R. E. Russell, J. Rotella, and J. G. Dudley (2011). Modeling nest survival of cavity-nesting birds in relation to postfire salvage logging. Journal of Wildlife Management 75:794–804. Close ). In Washington State, nest predation was higher in unburned stands (37% of 41 nests) compared to burned stands (30% of 45 nests) and overall nest survival was 41% in unburned and 80% in burned stands (214 Kozma, J. M., and A. J. Kroll (2012). Woodpecker nest survival in burned and unburned managed ponderosa pine forests of the northwestern United States. Condor 114:173–184. Close ). In partly harvested woodlots in southern Ontario, apparent nest success was relatively high, at 81% (n = 69), and Mayfield success was 0.76 (256 Straus, M. A., K. Bavrlic, E. Nol, D. M. Burke, and K. A. Elliott (2011). Reproductive success of cavity-nesting birds inpartially harvested woodlots. Canadian Journal of Forest Research 41:1004–1017. Close ). In this latter study, nests higher above ground and in larger and healthier trees were more successful. On a study site in Idaho, nest predation rates were relatively high, with 12 of 20 nests (60%) lost, with predation by weasels implicated as a main cause (257 Sadoti, G., T. J. Rodhouse, and K. T. Vierling (2010). Spatial dependence in Northern Flicker habitat-reproduction relationships: An application of Dutilleul's modified t-test. Condor 112:363–368. Close ).

Nest loss rate increased during the breeding season in Washington State (214 Kozma, J. M., and A. J. Kroll (2012). Woodpecker nest survival in burned and unburned managed ponderosa pine forests of the northwestern United States. Condor 114:173–184. Close ) whereas in central British Columbia, the loss rate reached a peak in the mid-breeding season (206 Fisher, R. J., and K. L. Wiebe (2006). Nest site attributes and temporal patterns of northern flicker nest loss: effects of predation and competition. Oecologia 147(4):744–753. Close ).

At Riske Creek, among nests surviving to hatching (n = 1,505), the average brood size just after hatching averaged 0.90 smaller than the clutch size (KLW) because some eggs fail to hatch. Most unhatched eggs appeared infertile, with no embryo or blood spots when cracked open (KLW). Among these nests, the average number of fledglings produced was 5.46 ± 2.4 SD (KLW) which was about one nestling less than at hatching, suggesting that on average one nestling is lost during the brood-rearing period (e.g., through starvation). In Nebraska and Wyoming, mean brood size (10–17 d posthatch) varied from 5.86 to 7.22, or about one less than clutch size (234 Moore, W. S., and W. D. Koenig (1986). Comparative reproductive success of Yellow-shafted, Red-shafted, and hybrid flickers across a hybrid zone. Auk 103:42–51. Close ).

Number of Broods Normally Reared per Season

Apparently single-brooded, but this needs confirmation in other color-banded populations.

Survivorship appears lower, on average, than that of many other woodpecker species (250 Wiebe, K. L. (2006). A review of adult survival rates in woodpeckers. Annales Zoologici Fennici 43(2):112–117. Close ). Based on banding and recovery data conducted during 18 breeding seasons at Riske Creek in central British Columbia, the oldest male was 10 years old (1 of 1,564 individuals) and the three oldest females were 9 years old (3 of 1,525 individuals) (252 Wiebe, K. L. (2018). Age-related improvements in fecundity are driven by the male in a bird with partially reversed sex roles in parental care. Oecologia 188:1095–1104. Close ). The maximum longevity reported from U.S. Geological Survey Bird Banding Lab data is 9 yr, 2 mo (258 Clapp, R. B., M. K. Klimkiewicz, and A. G. Futcher (1983). Longevity records of North American birds: Columbidae through Paridae. Journal of Field Ornithology 54:123–137. Close ).

Annual survivorship of adults (> 1 year old, ages and sexes pooled) was 0.43 (95% CI: 0.38–0.48) (249 Fisher, R. J., and K. L. Wiebe (2006). Effects of sex and age on survival of Northern Flickers: A six-year field study. Condor 108(1):193–200. Close ). The estimated apparent survival from the Monitoring Avian Productivity and Survivorship (MAPS) program, based on standardized mist-netting efforts, was 0.47 although this should be viewed with caution owing to the small sample size of recoveries (259 DeSante, D. F., D. R. Kaschube, and J. F. Saracco (2015). Vital rates of North American landbirds. Institute for Bird Populations, Point Reyes Station, CA, USA. Close ). Survival at Riske Creek depended on the North Atlantic Oscillation, a large-scale climactic pattern which might have affected conditions on the wintering grounds or during migration, but survival did not depend on sex or hybrid phenotype (51 Flockhart, D. T. T., and K. L. Wiebe (2008). Variable weather patterns affect annual survival of Northern Flickers more than phenotype in the hybrid zone. Condor 110:701–708. Close ).

The daily survival estimate for juveniles based on following 29 fledglings fitted with radio-transmitters for 22 days immediately post-fledging was 0.996 ± 0.004, which projects to 0.64 survival at the end of 2 months (248 Gow, E. A., and K. L. Wiebe (2014). Survival and habitat selection by fledgling northern flickers in a fragmented forest landscape. Journal of Wildlife Management 78:273–281. Close ). There are no good survival estimates for the first year of life due to the high natal dispersal and lack of band recoveries.

Body Parasites

Endoparasitic coccidian protozoans in the genus Isospora were isolated from the intestinal contents of a Northern Flicker during necropsy (260 Rejman, E. E., K. Hák-Kovács, and J. R. Barta (2022). The first Isospora species (Apicomplexa: Eimeriidae) described from the northern yellow-shafted Flicker (Colaptes auratus luteus) in Ontario, Canada. Acta Parasitologica 67:1162–1171. Close ), but their prevalence in wild populations is unknown. A nesting female flicker was heavily infested with coelomic nematodes (Diplotriaena) and acanthocephalid worms in the intestine (261 Gullion, G. W. (1949). A heavily parasitized flicker. Condor 51(5):232. Close ). Avian malaria, a blood parasite, has also been described in the Northern Flicker (262 Tierra, C. G., T. J. Lorenz, T. A. Lezhova, G. Valkiūnas, and R. N. M. Sehgal (2022). Description and molecular characterization of novel Leucocytozoon parasite (Apicomplexa: Haemosporida: Leucocytozoidae), Leucocytozoon polynuclearis n. sp. found in North American woodpeckers. Systematic Parasitology 99:103–114. Close ).

In terms of ectoparasites, Northern Flickers may have feather mites including Stenopteronyssus proctorae (263 Mironov, S. V., and T. D. Galloway (2006). New and little-known species of feather mites (Acari : Analgoidea : Pteronyssidae) from birds in North America. Canadian Entomologist 138(2):165–188. Close ). They also harbor several species of chewing lice, including Menacanthus pici, Penenirmus jungens, and Picicola porisma, with prevalence ranging from 38–85% and intensities ranging from 0–1,359 lice per bird depending on species of louse (264 Galloway, T. D., and R. J. Lamb (2016). Chewing lice (Phthiraptera: Amblycera and Ischnocera) infesting woodpeckers and sapsuckers (Aves: Piciformes: Picidae) in Manitoba, Canada. Canadian Entomologist 148:520–531. Close , 265 Lamb, R. J., and T. D. Galloway (2018). Abundance and stability of populations of chewing lice (Phthiraptera: Amblycera and Ischnocera) infesting two species of woodpeckers (Aves: Piciformes: Picidae). Canadian Entomologist 150:180–189. Close ). The Northern Flicker was among the bird species recorded as having ticks although the prevalence and number was not reported (266 Scharf, W. C., L. Aukland, G. W. Shugart, and S. A. Hamer (2020). Occurrence of Ticks (Acari: Ixodidae) on Birds in Northwestern Lower Michigan, 2011–2019. Great Lakes Entomologist 53(2)126–137. Close ). Both adults and nestlings may host blood sucking flies in the family Hippoboscidae which sometimes emerge from the feathers during banding (KLW); the species Ornithoica vicina was identified on Northern Flickers in Wisconsin at a prevalence of 2.5% of 197 individuals (267 Mueller, N. S., H. C. Mueller, and D. D. Berger (1969). Host records and phenology of louse-flies on Wisconsin birds. Wisconsin Academy of Sciences, Arts and Letters 57:189–207. Close ).

At Riske Creek in British Columbia, nearly all nestlings become infested with the ectoparasite fly Carnus hemapterus which congregates in the skin folds and wing pits of the developing young. Intensity of parasites increases rapidly during the first week of the nestling period, reaching an average intensity of 15.1 ± 8.3 SD flies per nestling in the second week (268 Wiebe, K. L. (2009). Nest excavation does not reduce harmful effects of ectoparasitism: an experiment with a woodpecker, the northern flicker Colaptes auratus. Journal of Avian Biology 40:166–172. Close ). Experimental fumigation of nests to rid them of Carnus flies resulted in higher fledging masses; however, freshly excavated nests did not offer health benefits because parasite prevalence was no different from that in reused cavities (268 Wiebe, K. L. (2009). Nest excavation does not reduce harmful effects of ectoparasitism: an experiment with a woodpecker, the northern flicker Colaptes auratus. Journal of Avian Biology 40:166–172. Close ). Blowflies (Protocalliphora lata) are detected in a relatively small percentage of nests (< 5% annually) (KLW). More studies are needed to quantify the prevalence and reproductive consequences of various endoparasites and ectoparasites.

Disease

West Nile Virus was reported from a Northern Flicker in California (269 Morgan, T., C. Fogarty, A. Pong, A. Trinidad, K. Nguyen, L. Krueger, R. Cummings, and M. Jozan (2015). Relevance of RT-qPCR cycle threshold values and antibody titers in free-ranging birds to the endemic/epidemic profile of West Nile virus transmission in Orange County, California. Proceedings and Papers of the Mosquito and Vector Control Association of California 83:57–60. Close ).

Exposure

Rarely (e.g., in about 1% of nests), nestlings may die as a result of the cavity being flooded by rain (KLW).

Predation

About 18–20% of nests annually were lost to predators (primarily red squirrel [Tamiasciurus hudsonicus]) at Riske Creek, British Columbia (206 Fisher, R. J., and K. L. Wiebe (2006). Nest site attributes and temporal patterns of northern flicker nest loss: effects of predation and competition. Oecologia 147(4):744–753. Close ). An average of 9% of radio-tagged Northern Flicker adults was killed while foraging by avian predators during the 3 months they were monitored during the breeding season (156 Elchuk, C. L., and K. L. Wiebe (2002). Food and predation risk as factors related to foraging locations of Northern Flickers. Wilson Bulletin 114(3):349–357. Close ). For a list of nest of predators, see Behavior: Predation.

Disease

West Nile Virus has been reported from a Northern Flicker in California (269 Morgan, T., C. Fogarty, A. Pong, A. Trinidad, K. Nguyen, L. Krueger, R. Cummings, and M. Jozan (2015). Relevance of RT-qPCR cycle threshold values and antibody titers in free-ranging birds to the endemic/epidemic profile of West Nile virus transmission in Orange County, California. Proceedings and Papers of the Mosquito and Vector Control Association of California 83:57–60. Close ), but no information on population-level impacts.

Direct Human Impacts

The Northern Flicker was among the 25 most common bird species to be struck by wind turbines in some parts of North America, but not in others (270 Allison, T. D., and R. Butryn (2019). A summary of bird fatality data in a nationwide database. American Wind Wildlife Institute Technical Report. Close ). It can also fall victim to colliding with windows (271 Schneider, R. M., C. M. Barton, K. W. Zirkle, C. F. Greene, and K. B. Newman (2018). Year-round monitoring reveals prevalence of fatal bird-window collisions at the Virginia Tech Corporate Research Center. PeerJ 6:e4562. Close ) and communications towers (148 Johnston, D. W., and T. P. Haines (1957). Analysis of mass bird mortality in October 1954. Auk 74:447–458. Close ). Study is needed on the population-scale impacts of collision-related mortality.

Anecdotal deaths from pesticides are reported (272 Fleischli, M. A., J. C. Franson, N. J. Thomas, D. L. Finley, and W. Riley Jr. (2004). Avian mortality events in the united states caused by anticholinesterase pesticides: A retrospective summary of National Wildlife Health Center records from 1980 to 2000. Archives of Environmental Contamination and Toxicology 46(4):542–550. Close ), but there is presently no evidence that populations are particularly at risk from chemicals.

Individual Distance

Information needed.

Territory Size

Defends an area around the nest tree, but does not defend a classic feeding territory probably because their main prey (ants) are not economically defendable (167 Elchuk, C. L., and K. L. Wiebe (2003). Ephemeral food resources and high conspecific densities as factors explaining lack of feeding territories in Northern Flickers (Colaptes auratus). Auk 120(1):187–193. Close ). The size of the defended area around the nest tree may depend on the stage of breeding and on snag densities, but more information needed. The shortest distance between two nests at Riske Creek was 5 m (two pairs breeding in adjacent trees), and active nests 30–50 m apart were not rare (KLW). This suggests a defense radius of between 5–25 m around the cavity tree. Distances between nests are determined by agonistic behavior but also depend on snag density, so one must be cautious about inferring territory size from distances between nests. With that caveat, in riparian woodlands with many snags in western Nebraska, the average distances among nearest-neighbor nests was 103 m (range 20–241, n = 19 nests; WSM, unpublished data 1982–1984). At a New Hampshire beaver pond, 3 active nests were 16, 70, and < 70 m apart (133 Kilham, L. (1983). Life history studies of woodpeckers of eastern North America. Publications of the Nuttall Ornithological Club 20, Cambridge, MA, USA. Close ). In southern Ontario, pairs nesting in two adjacent territories had nests separated by an average of 253 m, averaged over 3 years (146 Lawrence, L. D. (1966). A comparative life-history study of four species of woodpeckers. Ornithological Monographs 5. Close ). See also Agonistic Behavior: Territorial Behavior.

Home Range Size

Conducts its normal activities in undefended home ranges during both nonbreeding and breeding seasons. In late winter, 4 individuals in Colorado occupied home ranges of 48‒101 ha (134 Royall, W. C., Jr., and O. E. Bray (1980). A study of radio-equipped flickers. North American Bird Bander 5(2):47–50. Close ). Monitoring radio-tagged birds during the breeding season at Riske Creek, British Columbia revealed home ranges (95% convex polygons) of 5‒109 ha (mean 25 ha, n = 52) (155 Elchuk, C. L., and K. L. Wiebe (2003). Home-range size of northern flickers (Colaptes auratus) in relation to habitat and parental attributes. Canadian Journal of Zoology 81(6):954–961. Close ). Home ranges did not differ in size between the sexes (162 Gow, E. A., and K. L. Wiebe (2014). Northern flicker mates foraging on renewing patches avoid competition not by separate niches but by segregation. Behavioral Ecology and Sociobiology 69:101–108. Close ). See Agonistic Behavior: Territorial Behavior.

Numbers

The Northern Flicker is widespread and common across much of North America. Using data from the North American Breeding Bird Survey (BBS) the population was estimated at 11,000,000 individuals (95% CI: 10–12 million) for the United States and Canada for 2006–2015; the global population was estimated at 12,000,000 (251 Partners in Flight (2020). Population Estimates Database, version 3.1. Close ). Point-count abundance data collected by breeding bird atlas projects estimated populations at 700,000 individuals in Ontario for 2001–2005 (273 Cadman, M. D., D. A. Sutherland, G. G. Beck, D. Lepage, and A. R. Couturier (Editors) (2007). Atlas of the Breeding Birds of Ontario 2001–2005. Bird Studies Canada, Environment Canada, Ontario Field Ornithologists, Ontario Ministry of Natural Resources, and Ontario Nature, Toronto, Ontario, Canada. Close ), 354,800 birds (95% CI: 290,900–442,900) in West Virginia (274 Bailey, R. S., and C. B. Rucker (Editors) (2021). The Second Atlas of Breeding Birds in West Virginia. Pennsylvania State University Press, University Park, PA, USA. Close ), 187,000 birds (95% CI: 177,000–197,000) in Pennsylvania for 2004–2009 (275 Wilson, A. M., D. W. Brauning, and R. S. Mulvihill (Editors) (2012). Second Atlas of Breeding Birds in Pennsylvania. Pennsylvania State University Press, University Park, PA, USA. Close ), and 185,000 birds (95% CI: 165,000–205,000) in Ohio for 2007–2011 (276 Rodewald, P. G., M. B. Shumar, A. T. Boone, D. L. Slager, and J. S. McCormac (Editors) (2016). The Second Atlas of Breeding Birds in Ohio. Pennsylvania State University Press, University Park, PA, USA. Close ). Generally speaking, higher abundances during the breeding season occur in forested regions of the western United States, southwestern Canada, and the Great Lakes region (see Movements and Migration). However, abundances on a continental scale do not necessarily reflect local densities within habitats; e.g., breeding Northern Flickers are abundant in woodland habitat on the Great Plains (Habitat in Breeding Range), but such woodland habitat is sparse.

Reported densities of breeding Northern Flickers include: ponderosa pine forest (Arizona), 1 individual/4 ha (mean for 3 plots before snag removal; 277 Scott, V. E., and J. L. Oldemeyer (1983). Cavity-nesting bird requirements and responses to snag cutting in ponderosa pine. In Snag Habitat Management: Proceedings of the Symposium (J. W. Davis, G. A. Goodwin, and R. A. Ockenfels, Editors), U.S. Forest Service Geneneral Technical Reports RM-99. pp. 19–23. Close ); pine–fir forest (California), 1 pair/111 ha on unburned plots (mean for 5 plots; 118 Raphael, M. G., and M. White (1984). Use of snags by cavity-nesting birds in the Sierra Nevada. Wildlife Monographs 86:1–66. Close ); burned forest plots in Idaho, 1 pair/22.5 ha (unlogged), 1 pair/38 ha (salvage logged; 278 Saab, V. A., R. E. Russell, and J. G. Dudley (2007). Nest densities of cavity-nesting birds in relation to postfire salvage logging and time since wildfire. Condor 109:97–108. Close ). At Riske Creek, British Columbia, average densities were about 1 pair/50 ha (over a 7,500 ha tract of grassland and patchy forest, KLW), but localized densities can be much higher in larger groves of trembling aspen (Populus tremuloides) (see 167 Elchuk, C. L., and K. L. Wiebe (2003). Ephemeral food resources and high conspecific densities as factors explaining lack of feeding territories in Northern Flickers (Colaptes auratus). Auk 120(1):187–193. Close ).

Maximum winter abundances (individual birds observed/party hour) based on Christmas Bird Counts (CBC): Yellow-shafted Flicker 2.77/h, with maximum abundance along river valleys and coastal plains, below 305 m; Red-shafted Flicker 4.72/h, with maximum abundance in river valleys, but more abundant at higher elevations than Yellow-shafted Flicker (279 Root, T. (1988). Atlas of Wintering North American Birds: An Analysis of Christmas Bird Count Data. University of Chicago Press, Chicago, IL, USA. Close ).

Trends

Trends vary according to geographic location and time frame analyzed and are conflicting. Long-term population trends from the BBS (1966–2019) indicated a 1.2% annual decline (95% CI: –1.4, –1.0; n = 4,391 survey routes) averaged across the BBS survey region in Canada and the United States (280 Sauer, J. R., W. A. Link, and J. E. Hines (2020). The North American Breeding Bird Survey, Analysis Results 1966–2019. U.S. Geological Survey data release. Close ; Figure 8). During that time frame, significant declines occurred in 40 of 58 (70%) states and provinces, and there were no significant increases. Decreases are focused in the eastern and central United States; considering the time frame from 1993–2019, an annual decline averaging 1.59% occurred in central and eastern North America while populations in the West showed no trend (280 Sauer, J. R., W. A. Link, and J. E. Hines (2020). The North American Breeding Bird Survey, Analysis Results 1966–2019. U.S. Geological Survey data release. Close ), however, the statistical confidence of any trends was rated as "low" for all geographic regions. Thus, it is possible that yellow-shafted subspecies is declining in the south-central and southeastern regions of North America, whereas there may be no ongoing trend for red-shafted populations in the West. A more recent long-term survey in Alaska indicated that the Northern Flicker (red-shafted group) was increasing there (281 Handel, C. M., and J. R. Sauer (2017). Combined analysis of roadside and off-road breeding bird survey data to assess population change in Alaska. Condor 119:557–575. Close ). Christmas Bird Count (CBC) data from Nebraska showed a significant increase in the number of overwintering Northern Flickers during the period 1992–2020 (282 Gubanyi, J. A. (2020). History of the Seward-Branched Oak Lake Christmas Bird Count,1993–2020. Nebraska Bird Review 88:162–172. Close ), consistent with CBC data for Northern Flickers overwintering in the Great Plains (283 Johnsgard, P. A., and T. G. Shane (2009). Four decades of Christmas Bird Counts in the Great Plains: ornithological evidence of a changing climate. Papers in Ornithology 46. Close ).

Because Northern Flickers require an appropriate substrate for nesting (a dead or declining tree of sufficient girth), the density of some populations may be limited by the availability and spacing of suitable nest sites (124 Aitken, K. E. H., K. L. Wiebe, and K. Martin (2002). Nest-site reuse patterns for a cavity-nesting bird community in interior British Columbia. Auk 119:391–402. Close , 232 Wiebe, K. L. (2014). Responses of cavity nesting birds to fire: testing a general model with data from the northern flicker. Ecology 95:2537–2547. Close ). Carefully designed experiments are needed to determine whether cavity abundance is limiting for a population (284 Wiebe, K. L. (2011). Nest sites as limiting resources for cavity-nesting birds in mature forest ecosystems: A review of the evidence. Journal of Field Ornithology 82:239–248. Close ). The density of Northern Flickers decreased on an experimental plot where ponderosa pine was harvested and snags were removed, but increased on a harvested plot where snags were left and on a control plot that was not harvested (277 Scott, V. E., and J. L. Oldemeyer (1983). Cavity-nesting bird requirements and responses to snag cutting in ponderosa pine. In Snag Habitat Management: Proceedings of the Symposium (J. W. Davis, G. A. Goodwin, and R. A. Ockenfels, Editors), U.S. Forest Service Geneneral Technical Reports RM-99. pp. 19–23. Close ). Similarly, density decreased to half its pretreatment level when snags were removed from a burned pine–fir site in California, and density was at least 5 times as high in the burned forest as at any unburned site (118 Raphael, M. G., and M. White (1984). Use of snags by cavity-nesting birds in the Sierra Nevada. Wildlife Monographs 86:1–66. Close ).

Because the Northern Flicker is associated with open habitats and open woodlands, disturbances (either natural or human caused) that open up a dense forest canopy have been linked to population increases. For example, numbers increased after a pine beetle outbreak and the associated selective logging at Riske Creek, British Columbia (285 Drever, M. C., and K. Martin (2010). Response of woodpeckers to changes in forest health and harvest: Implications for conservation of avian biodiversity. Forest Ecology and Management 259(5):958–966. Close , 286 Edworthy, A. B., M. C. Drever, and K. Martin (2011). Woodpeckers increase in abundance but maintain fecundity in response to an outbreak of mountain pine bark beetles. Forest Ecology and Management 261(2):203–210. Close ). In the Okanagan region of British Columbia, densities increased during 3–8 years after a wildfire that opened up the forest canopy (287 Gyug, L. W. (2013). Effects of fire on bird abundance in Okanagan Mountain Provincial Park, British Columbia. British Columbia Birds 23:16–26. Close ). At Riske Creek, breeding densities increased 1.77-fold in the short term (1–3 years) after wildfires but declined to baseline levels once burnt snags began to fall (216 Wiebe, K. L. (2017). Northern flickers only work when they have to: how individual traits, population size and landscape disturbances affect excavation rates of an ecosystem engineer. Journal of Avian Biology 48:431–438. Close ). In general, populations show little response to forest insect outbreaks compared to other woodpeckers because their main prey is ground-dwelling ants. Based on a variety of study areas in western Canada and the United States, density showed no consistent trend with outbreaks of mountain pine beetle although they did increase on plots that were salvage-logged (288 Saab, V. A., Q. S. Latif , M. M. Rowland, T. N. Johnson, A. D. Chalfoun, S. W. Buskirk, J. E. Heyward, and M. A. Dresser (2014). Ecological consequences of mountain pine beetle outbreaks for wildlife in western North American forests. Forest Science 60:539–559. Close , 289 Mosher, B. A., V. A. Saab, M. D. Lerch, M. M. Ellis, and J. J. Rotella (2019). Forest birds exhibit variable changes during a mountain pine beetle epidemic. Ecosphere 10(12):e02935. Close ). Daily nest survival rates also did not vary according to pine beetle outbreak (290 Saab, V. A., Q. S. Latif, M. A. Dresser, and J. G. Dudley (2019). Woodpecker nest survival, density, and a pine beetle outbreak. Journal of Wildlife Management 83:1387–1400. Close ), and densities did not respond to gypsy moth outbreaks in the short term (291 Koenig, W. D., E. L. Walters, and A. M. Liebhold (2011). Effects of gypsy moth outbreaks on North American woodpeckers. Condor 113(2):352–361. Close ). Thus, whereas the availability of snags seems to have a clear role in determining population densities, studies are needed to test whether the availability of food (ants and other terrestrial insects) ever regulates Northern Flicker population sizes.

Competition with other cavity-nesting species may also influence population density. Competition with the European Starling is often evoked as an explanation for dwindling numbers of the Northern Flicker (see Management and Effects of Human Activity).