Species names in all available languages
|Bulgarian||Златист шилоклюн кълвач|
|English (United States)||Northern Flicker|
|French (France)||Pic flamboyant|
|Lithuanian||Paprastasis ylasnapis genys|
|Serbian||Američka zlatokrila žuna|
|Spanish (Cuba)||Carpintero escapulario|
|Spanish (Honduras)||Carpintero de Ocotal|
|Spanish (Mexico)||Carpintero de Pechera Común|
|Spanish (Spain)||Carpintero escapulario|
Karen L. Wiebe revised the account. Peter Pyle contributed to the Plumages, Molts, and Structure page. Peter F. D. Boesman contributed to the Sounds and Vocal Behaviors page. Arnau Bonan Barfull curated the media. JoAnn Hackos, Robin K. Murie, and Daphne R. Walmer copyedited the account. Eliza Wein revised the distribution map.
Colaptes auratus (Linnaeus, 1758)
- auratum / auratus
The Key to Scientific Names
Northern Flicker Colaptes auratus Scientific name definitions
Version: 2.0 — Published July 7, 2023
Account navigation Account navigation
The Northern Flicker is characterized by a "fast" life-history with larger clutches than most other woodpeckers and a relatively short lifespan. Most individuals appear to attempt breeding as yearlings and every year thereafter. Both sexes are involved at all stages of nesting, but the species has partially-reversed sex roles, with the male contributing more parental care than the female.
Few observations; more studies are needed with banded birds. In Iowa and Kansas, courtship starts about mid-April with pair formation by the end of April or early May (145, 210). At Riske Creek in central British Columbia, territory establishment and pair formation probably happen concurrently and shortly after arrival on the breeding site after migration (i.e., mid-April to early May; KLW). Divorced birds initiated laying later than birds pairing with the same partner from the previous year, suggesting that renewing a former pair-bond took less time than establishing a new pair (190). Phenology for subspecies in Cuba, Grand Cayman Island, and Guatemala is poorly known. In Guatemala, flickers seemed to pair by early February with egg-laying probably starting about 1 March (211). On Grand Cayman Island, breeding occurred between January and August with peaks from March to July; it was claimed that pair bonds were retained most of the year (212), although without color-banded individuals, the evidence for this is not clear.
Figure 1. At Pimsi Bay, Ontario, mean starting date for nest-cavity excavation was 9 May (range 29 April–15 May, n = 10; 146). For southeastern Wisconsin, mean starting date was 17 April (range 2 April–23 May, n = 13; 193). Duration of excavation period was 12.1 d for Ontario (range 5–19, n = 7; 146) and 15.2 d for Wisconsin (range 11–20, n = 13; 193).
First Brood/Only Brood
There are no confirmed records of second broods and this would be hard to determine without color-banded individuals. However, the relatively long breeding cycle of the Northern Flicker means that only one brood can probably be raised in most of the geographic range (213), but a pair may renest if their first clutch is destroyed. In central British Columbia, the annual mean laying date in the population was negatively correlated with temperature on the study area from 20 April–4 May (i.e., during the period shortly before egg laying), becoming 1.15 days earlier for every degree warmer during that spring period (152). Because there is little activity of ants on the ground surface at ambient temperatures < 5°C (159) and female flickers probably depend on a sufficient abundance of ants to increase body condition and lay eggs, it makes sense that the timing of egg laying is correlated with ambient temperatures and probably latitude. During 12 years at Riske Creek (ca. 52°N), the average initiation date for clutches (n = 1,182) was 14 May (range 26 April–13 June; 152). In Washington state (46°N), the mean laying date was 17 May (range 1 May–13 June, n = 47, 214). In Nebraska (ca. 41°N) from 1982–1994, modal date in different years for first egg laid was 9–18 May (range 1 May–1 June, n = 30; WSM). In Wyoming (42°N) and New Mexico (34°N), modal dates were 7–12 May and 1–6 May, respectively (WSM). The latest initiation date of a replacement clutch at Riske Creek was 2 July (KLW).
Not well understood. Some have reported that the female chooses the nest site (172, 133), while others concluded that the male did (145, 193). Ritualized tapping (see Nonvocal Sounds) may communicate information between pair members regarding acceptability of a nest site. Individuals are usually philopatric to home ranges, but not necessarily to nest trees (137, 190). Nest cavities are frequently reused (215). Indeed, based on 1,843 first nests over 18 years of study at Riske Creek, an average of only 23% were freshly excavated that year; the majority were placed in existing (reused) holes (216). The frequency of freshly excavated nests declined seasonally, suggesting that flickers are more likely to select existing holes when faced with time constraints for breeding (216).
Usually excavates nest cavities in dead or diseased tree trunks and large branches. Wood hardness was the primary factor determining which trees were selected on home ranges and where on the tree the nest was excavated (217) but the Northern Flicker can use a wide breadth of decay classes of trees (218). It uses a diversity of tree species but prefers trembling aspen (Populus tremuloides) over more abundant conifer species (96% of nests at Riske Creek were in aspens; 123, 5). Probably the typical heart rot in mature aspens makes them easier to excavate (219). In El Salvador, the Guatemalan Flicker (subspecies ) usually nests in tall dead pine trees, sometimes in half-rotten oak stubs (211). In Miami, Florida, 58% of 40 nests were placed in dead palm trees (220). In deserts it may nest in saguaro cacti (Carnegiea gigantea) and may usurp or enlarge cavities in cacti originally made by Gila Woodpecker (Melanerpes uropygialis) (221). Rarely may nest in earthen burrows; e.g., used nest burrows of Belted Kingfisher (Megaceryle alcyon) or Bank Swallow (Riparia riparia) (222). There are a handful of reports of Northern Flickers nesting directly on the ground, a review of cases is in (223), but no such nest has been successful.
In Wisconsin, 92% of nest cavities were in dead trees (193); in Ontario 76% (146), similar to the 74% reported by (224). In British Columbia 53% (n = 160) were in dead trees and most other nests in diseased trees (123). In Sierra Nevada Mountains., 78% of 68 nests were in snags, 20% in dead portions of live trees, 2% in live portions of live trees (118). On Nantucket Island, Massachusetts, 87.5% in trees, 12.5% in other structures (mostly buildings); of nests in trees, 62% were in dead trees, 4% in dead branches of live trees (222). In Ohio, 63.6% of nests were in dead trees, 36.4% were in live trees, and 79.5% (total) were in dead limbs (n = 44; 225). Along the South Platte River (Colorado), only 27% of nest cavities were in dead trees, although a total of 61% were in dead substrate (119). When Northern Flickers excavate in live trees, they often use knotholes (58% of cavities) formed by broken limbs as starting points presumably because these are starting points for decay (119).
Nest height above ground is variable. Average nest cavity heights: Wisconsin 5.7 m (range 3–10, n = 16; 193); Ontario 7.0 m (range 2.4–13.7, n = 25; 146); Iowa 8.1 m ± 3.2 SD (n = 31; 226); Ohio 8.4 m ± 0.65 SD (n = 44; 225); and Wyoming 7.3 m ± 0.6 SD (n = 28; 224). Significantly lower average heights on Nantucket Island, Massachusetts, where trees are scrubbier: 1.3 m (range 0.0–5.18, n = 169; 222), but greater heights in tall Douglas-fir (Pseudotsuga menziesii) in western Oregon: 11.4 m (range 3.0–26.8, n = 8; 117).
May use nestboxes especially where natural cavities are scarce. However, only one pair was ever recorded in the 50 nestboxes placed at Riske Creek over the duration of the study. Natural holes are abundant at Riske Creek so such cavities were clearly preferred over boxes.
Both sexes participate in cavity excavation, but the male plays dominant role. During cavity excavation in Ontario, either male or female excavated 40% of observation time (795 mins, 10 nests): male 68% of excavation time, female 32% (146). In Wisconsin, males performed 88% of excavation at 12 nests (193). In New Hampshire, the male of a pair observed did 81% of the excavating (133). Female participation appears to increase toward the end of excavation (146, 133, 193). The nest cavity is excavated by “chiseling” away small chips of wood with bill; the bird starts by clinging to the trunk, using its tail as a prop, then perching on the lower lip of the nest opening as it works its way into the interior. Periods of chiseling are interspersed with shorter periods of tossing chips from the cavity opening; chips are also carried away in the bill.
No detailed data on diurnal distribution of excavation activity, but nest excavation observed throughout daylight hours. Length of time to build a nest is highly variable, depending on whether it is a new excavation, hardness of wood, and intensity of excavation effort. Mean excavation time in Ontario was 12.1 d (range 5–19, n = 10; 146); in Wisconsin 15.2 d (range 11–20, n = 15; 193). Lawrence (146) reported short and irregular periods for 16 observed periods of excavation; e.g., mean minimum duration: male 13.3 (range 1–50), female 19.7 (range 3–40). Kilham (133) described two nest excavations, one in which the male did 81% of excavation and worked 60–80 min at a stretch, and the other in which the female did the most excavation and worked for periods up to 85 min.
Structure and Composition
The cavity curves quickly downward beyond the entrance, and the diameter rapidly expands beyond the entry hole; the front wall is typically < 2.5 cm thick. The cavity is usually cylindrical with a slightly concave floor. The entrance is typically just large enough to accommodate the entry and exit of adults; the interior is large enough for adults to turn around. Eggs are laid directly on a bed of wood chips.
Average horizontal diameter of entrance holes reported from various locales: 8.33 cm (132); 7.3 cm ± 0.21 SE in Ohio (n = 32; 225); 6.58 cm ± 0.21 SE in Wyoming (n = 28; 224); 6.9 cm ± 0.5 SE in central British Columbia (n = 14; 227); and 6.45 cm ± 0.03 SE at Riske Creek in central British Columbia (n = 596; KLW). Vertical diameters are often slightly longer. Interior diameter of the cavity near the bottom floor: 19.48 cm (132) and 14.6 cm ± 0.11 SE (n = 559; KLW). Vertical depth from entrance to floor: 40.11 cm (range 15.24–91.44; 132), 33.7 cm ± 2.5 SE (227), and 39.0 cm ± 0.53 SE (n = 584; KLW). Breadth (inside edge of entrance to back wall): 14.9 cm ± 0.6 SE, and floor area 158 cm2 ± 12 SE (227). Wiebe and Swift (228) reported a mean floor area of 166 cm2 ± 6.4 SE, but 3 extraordinarily large cavities in hollow trees had floor areas > 400 cm2 (see Table 1 in 123).
Nest tree and limb size variable. Diameter of tree at breast height: 46.9 cm ± 2.7 SE in Ohio (n = 42; 225); 30.0 cm ± 2.0 SE in British Columbia (n = 14; 227); 33.9 cm ± 0.81 SE in British Columbia (n = 160; 123); 46.3 cm ± 4.1 SE in Wyoming (n = 28; 224); and 31.9 cm ± 2.4 in British Columbia (n = 17; 219). Tree diameter at nest height: 34.5 cm ± 10.6 SD in Iowa (n = 31; 226); 27.1 cm ± 2.0 SE in Wyoming (n = 28; 224); and 31.3 cm ± 0.29 SE in British Columbia (n = 133; 123).
Dataloggers placed in cavities in central British Columbia just after nestlings fledged (123) showed that temperature fluctuations in cavities were less extreme than in the environment and reached a low of about 5°C between 0600–0700 h and as high as 32°C around 1750 h in July. Diel temperature variation was greatest in small diameter trees and in highly decayed trees. South-facing cavities reached the highest daytime temperatures, and entrances were oriented non-randomly towards the south, suggesting cavities were excavated to gain thermal advantages. The interior temperature of eight occupied cavities in Montana was fairly stable relative to ambient temperature and did not vary more than 5°C from the mean temperature of 20.4°C (229).
Other studies have also found that nest hole orientation is significantly skewed toward the East, Southeast, and South (n = 160 nests; data pooled from 146, 222, and 193). However, there was no significant bias reported for studies in Ohio (n = 44; 225) and Iowa (n = 31; 226).
Maintenance or Reuse of Nests
Northern Flicker tends to use existing nest cavities more frequently than most other woodpeckers but reuse is quite variable among populations (230). Before reuse, the Northern Flicker lays down a fresh bed of woodchips on the bottom by further excavating some of the interior wall. In Wisconsin, reuse was in 2 of 16 nests (13%; 193); Ohio, 20 of 44 (45.5%; 225); British Columbia, 63% of 739 (230). On the Great Plains (Nebraska, Colorado, Wyoming, New Mexico), of 14 individuals banded as adults and recovered in a subsequent breeding season, 3 reused the same nest cavity where they were captured for banding (WSM). Northern Flicker sometimes complete excavation of a nest cavity partially excavated in a previous year or it may renovate or enlarge cavities previously excavated by other species of woodpeckers (231). Propensity to excavate a new nest increased after wildfire destroyed 40% of the existing cavities at Riske Creek, British Columbia; fewer existing holes were available for reuse, and reused nests were more often in large, living trees because many of the dry, dead snags burned (232).
Ovate, varying to short-ovate, elliptical-ovate, nearly oval, and rarely somewhat pointed (9).
Given (in centimeters) as mean length × breadth (min, max), sample size. For the southern United States: 2.79 × 2.16 (2.29 × 1.91, 3.15 × 2.34), n = 133; for New England, New York, Ontario, and Pennsylvania: 2.77 × 2.17, n = 233; for Midwest (Ohio, Kentucky, Wisconsin, Kansas, Nebraska, Iowa, and Minnesota): 2.76 × 2.17 (2.36 × 1.65, 3.58 × 2.36), n =126 (132). In western North America: 2.82 × 2.19 (2.54 × 2.08, 3.56 × 2.03), n = 57; northwestern United States (northern California–Alaska): 2.93 × 2.24 (2.64 × 2.08, 3.20 × 2.34), n = 47 (9). In central British Columbia, egg length is 2.81 cm ± 1.6 SD, breadth 2.18 cm ± 1.1 SD, n = 288 (233); range (i.e., minimum–maximum measures) for length 1.86–3.65 cm, breadth 1.60–3.31 (KLW).
Abnormally small "runt" eggs are found in < 5% of clutches, typically as the first-laid egg of a sequence (KLW).
Mass and Composition
Based on 17 eggs from 3 clutches: 5.4 g ± 0.23 SD (145). From 27 eggs from 27 different clutches: 7.01 g ± 0.61 SD (233). Of the wet egg weight, the proportion of yolk (16%) is among the smallest of any bird species although lipid content of the yolk (58%) is similar to that of other altricial birds (233).
No data. Eggshells weighed on average 0.58 g (233).
Color and Surface Texture
Shell is pure lustrous white and semi-glossy but egg appears pinkish up to about the 5th day of incubation because the dark orange yolk shines through the shell before the embryonic membranes are formed (KLW).
Varies locally, latitudinally, and seasonally (see Measures of Breeding Activity). A pooled estimate based on clutches recorded from a range of latitudes in the United States was 6.5 ± 1.4 SD (range 3–12, n = 411; 234). At Riske Creek in central British Columbia (52° N), the size of first clutches was 7.99 ± 1.3 SD, n = 1579 and of second (replacement) clutches was 6.83 ± 1.1 SD, n = 266; for all clutches pooled: 7.81 ± 1.4 SD (range 2–13) n = 1,872 (KLW) . At a study site in Washington State (46.6° N), the average clutch was 7.0 (range 4–12, n = 82; 214). At four study sites on a transect across the hybrid zone in Nebraska and Wyoming (latitude 42°N), mean clutch sizes did not differ according to phenotype and were: Sutherland, Nebraska: 7.50 ± 1.53 SD (n = 26, nearly pure Yellow-shafted Flicker); Bridgeport, Nebraska: 7.16 ± 1.37 SD (n = 32, hybrid); Morrill, Nebraska 6.97 ± 1.28 SD (n = 32, hybrid); Wheatland, Wyoming: 7.75 ± 1.48 SD (n = 16, hybrid tending toward pure Red-shafted Flicker) (234). Clutches larger than 13 eggs are likely the result of conspecific brood parasitism.
Appears to begin shortly after completion of the nest, but detailed data are not available. Eggs are laid at a rate of 1 per day, usually between 05:00 and 06:00 h (145). Parental attentiveness at nest increases at onset of egg-laying, particularly by female, but male remains the most attentive. Based on 17 observation periods at 3 nests lasting 1 hour in length [in Colorado, Kansas, and New Mexico], one member of the pair was in the cavity 71% of the time during the egg-laying period (the male accounting for about 3/4 of the time in the cavity; WSM). One parent is usually in or near nest during egg-laying; pairs seem to switch nest-guarding duty as one leaves the area to forage (KLW).
Species is a well-known indefinite layer; i.e., when an egg is removed, it is replaced. Burns (132) and Bent (9) report numerous instances of oologists removing eggs singly and as whole clutches from Northern Flicker nests and the female replacing them. In one case, 1 egg was removed each day, and each day the female replaced the egg until a total of 71 eggs was laid (235). Relaying after destruction of a clutch may occur after 7 d (187).
Onset of Broodiness and Incubation in Relation to Laying
There have been no attempts to install thermometers in the nest bowl to directly measure the onset of incubation. However, the hatching span of eggs within a clutch, which typically varies from 1‒3 days (KLW) suggests incubation can begin on the ante-penultimate, penultimate, or last egg of the clutch. Because it is the male which incubates during the nighttime hours and during much of the day, presumably it is the broodiness of the male that largely determines the onset of embryonic development. Many (about 50%) of broods hatch "synchronously" within 24 hours (KLW). Based on direct observations of nests, Sherman (145) similarly suggested incubation begins 0–2 d before last egg is laid.
Both male and female develop a single, large oval patch in the belly region (KLW).
Based on Sherman's (145) detailed observations of 5 eggs, the average time for embryo development (onset of incubation on that egg to the hatching of that egg) was 11.9 d (range 11.2–12.4). Incubation onset is variable (see above) but in Sherman's case, this meant that nestlings hatched 9–10 d after last egg was laid. The oldest nestlings in a brood began to hatch 10.9 d on average after the last egg was laid in 174 clutches in central British Columbia (KLW); if incubation typically begins on the penultimate egg, this would equate to an embryonic development time of about 12 d, consistent with Sherman's estimate. Woodpeckers have a similar total development time from incubation to fledging as other altricial birds but their incubation period relative to the nestling period is 57% shorter (236). Yom-Tov and Ar (236) hypothesized that hypoxic conditions in tree cavities selected for early hatching; however, measurements of oxygen in tree cavities with incubating females inside did not reveal oxygen deficits sufficient to inhibit embryo development (237).
Incubation is shared by the male and female and transfers between partners take about 10–20 seconds at the nest hole such that the clutch remains covered about 98% of the time (188). Except in rare cases, the male does all nighttime incubation (145, 187). Based on continuous video monitoring during periods lasting 1–6 days at 71 nests at Riske Creek, British Columbia, the sexes switch off in 3–8 daytime bouts lasting 1.97 h ± 0.69 SD for males and 1.93 h ± 0.52 SD for females (188). The longest daytime incubation bout was 5.73 h by a male (KLW). Another estimate (sexes pooled) for daytime incubation bouts was 2.3 h based on nest observations (133). Between the sunrise and sunset incubation transfers (i.e., during daylight hours), the sexes contributed approximately equally to incubation but because males incubate at night, males do 67% of the total incubation on average (n = 71 nests; 188). Polyandrous females contributed less incubation at their secondary nest than a monogamous female because they were simultaneously feeding nestlings at their primary brood (188).
Large males (in terms of structural body size) and males in poor body condition incubated less than smaller males or those with good nutrient reserves (188). Incubation pattern and the proportional contribution by each sex did not influence the incubation period or hatching success of the clutch (188).
Hardiness of Eggs against Temperature Stress; Effect of Egg Neglect
Preliminary Events and Vocalizations
No conspicuous changes in behavior or vocalizations associated with hatching have been noted.
Shell-Breaking and Emergence
Based on casual observation, the process is similar to many other bird species: first a pip or "star crack" appears on the wide end of an egg. Then, the crack is gradually enlarges to encircle the egg so that the shell breaks in two as the nestling emerges (KLW).
Parental Assistance and Disposal of Eggshells
No data to indicate that the parents assist in hatching the eggs. Casual observations suggest that most parents (67–75%) remove eggshells from the nest within one day of hatching, but sometimes they are left in the cavity and may "cap" other eggs, causing hatching failure (KLW). Unhatched eggs are often left on the cavity bottom.
Condition at Hatching
Hatchlings are altricial―eyes closed and lacking down or feathers. The bill, tarsus, and feet are pale pinkish-yellow to pink. There is a white fleshy fold at the jaw hinge and calcareous white "egg teeth" on the tips of both the upper and lower maxillae which help the parents to locate the mouths of nestlings in the dark cavity (238). Unlike most other birds, these egg teeth are retained throughout the nestling period, being visible even in young about to fledge (238). Hatchlings aggregate on the floor of the nest cavity, craning their heads weakly when a parent enters nest. Mean body mass at hatching 5.46 g in Iowa (n = 3; 145), 5.50 g in Florida (n = 10; F. Lohrer, unpublished data); approximately 6 g in British Columbia (KLW). Linear measurements not reported.
Growth and Development
See Figure 7. From Sherman (145): mean body mass on day after hatching 11.8 g ± 3.0 SD; nestling growth roughly linear from day 2 to day 10 (77.8 g ± 8.8 SD on day 10). Growth slows from day 10 to day 18 (102.1 g ± 13.6 SD on day 15, 108.8 g ± 12.8 SD on day 18); mean weight is constant from day 19 to 25 (114.0 g ± 13.5 SD on day 25) but declines slightly just before fledging. The sexes are not distinguishable by size or mass at hatching; the logistic growth curves start to diverge for each sex around day 11, the time of maximum growth rate (see Gow et al. ). Near fledging, around day 25, males weigh about 6% more than females (239) but fledging mass for both sexes depends on brood size, peaking in a brood size of 4 and declining for larger broods. A pooled estimate of fledging mass: (male 134 g ± 0.48 SD, n = 565; female 127 g ± 0.45 SD, n = 606; KLW).
Tail and wing feathers grew at a rate of 4.09 mm/day and 3.75mm/day, respectively (239).
The following is a summary of the external appearance of nestlings at various ages, assuming hatching day = 0. Ages are approximate (± 2 d), because the hatching asynchrony within broods means that nestlings are of slightly different ages and may develop at slightly different rates. Descriptions are based on notes and photographs taken at study sites in British Columbia (KLW) and in the central United States (WSM).
Day 0. See Condition at Hatching, above.
Days 1–16. Appear as newly hatched but larger. Day 6: feather tracts first appear in hatchlings as dark gray swellings along the posterior edge of wing (alar tract) and tail-bud (caudal tract) and along anterior and midbody regions of back (dorsal tract, anterior and saddle elements). Days 7–8: flight feathers emerge from the skin as pin feathers. Days 10–11: eyes partially opened; feather vanes begin to erupt from tips of flight-feather shafts (extending approximately 2 mm out of shafts of tail feathers); femoral tract conspicuous with white-tipped feathers emerging; white feathers of dorsal rump patch (posterior element of dorsal tract) begin to emerge; crown appears gray as feathers of capital tract begin to emerge; bill, tarsus, and feet begin to turn from pinkish to gray; skin begins to turn from pale pinkish-yellow to darker purplish pink. Days 12–16: eyes fully open, contour feathers dramatically more conspicuous; black and brown dorsal plumage spots that form barred dorsal-plumage pattern of adult conspicuous; vanes extend 5–10 mm from shafts of tail feathers; crown nearly fully feathered but with narrow, central bare strip (apterium); bill, tarsus, and toes slate-gray color as in adult.
Days 17–23. Change primarily in extent of feather growth. Day 17: vanes of emerging flight feathers begin to unfold laterally, vanes of tail feathers extend 18–21 mm from shafts. Day 19: central crown apterium nearly closed but visible as a furrow; shaft color (yellow/red) apparent in dorsal shaft surface of flight feathers; malar stripe and nuchal patch apparent. Day 23: crown apterium closed to an inconspicuous furrow; vanes of tail feathers extend approximately 25 mm. Nestlings leave nest at 24–27 d, looking like small adults with softer plumage that is duller in color.
Nestlings huddle at bottom of nest until about 11 d old, then for about 1 week, they array themselves around the circumference at bottom of cavity with their chins and throats pressed against the wall; at 17–18 d they are strong enough and claws sharp enough to cling to the cavity walls (145). At approximately 16 d, the tips of bills can be seen at the nest hole, and heads can be seen at 21 d (133).
Sex Ratios and Sex Allocation
Based on the sexing of 8,321 nestlings banded over 16 years at Riske Creek, British Columbia, there was no sex bias among fledglings at the population level (49.8% males produced from 4,144 broods) (240). Older parents and those in better body condition did not produce more male nestlings (the larger sex). However, mothers allocated more of the cheaper sex (the smaller females) to last-hatching offspring in asynchronous broods, consistent with a strategy of trying to minimize brood reduction (240).
The nestling phase can be divided into 3 stages with regard to parental care: (I) 0–4 d since hatching, (II) 5–14 d, and (III) 15 d to nest departure. Both parents provide care in all phases, but total nest attendance and relative contributions of male and female change. Phase I is characterized by high parental attendance and rapid nestling growth; Phase II by reduced parental attendance but sustained rapid growth; and Phase III by infrequent parental attendance and slower nestling growth.
Data on nest temperature and thermal regulation is not available. Phase I of the nestling phase corresponds to intensive brooding because one adult is usually in the nest during the day, and the male broods during nightime hours (KLW). The number of day hours spent brooding declines during Phase II and is dependent on ambient temperature (161). When it was cold, each parent spent about 40% of their daylight time budget in the nest cavity when nestlings were 5–8 d old and brooding declined to about 20% of the daily time budget when nestlings were between 8–14 d old. Thus, nestlings could probably thermoregulate around 10 d. The amount of time parents spend inside the cavity declines rapidly after about day 15. Overall, males brooded slightly more than females during the nestling period (161) and, even when not inside the cavity, males spent more time closer to the nest (within 40 m) than females, possibly guarding the vulnerable offspring against predators.
Parents begin to feed the young by regurgitation shortly after hatching. The pharynx of adult expands to form a crop, which is engorged, particularly with ant larvae, when the adult returns to nest. The light colored phalanges and egg teeth of nestlings help parents to locate the gapes of nestlings at the bottom of the dark cavity (241). Both sexes feed young, usually with every visit to the nest; relative numbers of nest visits by male and female presumably reflect relative contributions to feeding. Sherman (145) weighed single loads fed to a single nestling on three occasions: 6.4 g. According to her observations, adults make approximately 10 feeding visits to nest on day 0, and this increases to 40–50 later in the nesting cycle. The male's provisioning rate increases from about 0.92 visits/h when nestlings are young and is still brooding to about 1.9 visits/h later in the nestling period, whereas the female's provisioning rate was positively correlated with brood size (239). On average, males provisioned at a slightly higher rate than females, especially during the mid-nestling period when the energy demand of the brood was the highest (239). Allocation of food within broods needs further study. Over a 4.5-hour observation period at a single nest on day 17, 5 nestlings received, on average, a feeding every 54 min; 3 nestlings received 5 feedings each, 2 nestlings received 4 feedings, and the recipient of 2 feedings could not be determined (145).
Parents, in the short-term, adjust provisioning rates to brood demands. Provisioning rates increased when the mate was experimentally removed (187); they increased when pairs were given experimentally enlarged broods and decreased when given reduced brood sizes (242). However, on a per-nestling basis, nestlings from enlarged broods did not receive as much food compared to the control or reduced broods, and they declined in mass (243, 242). Thus, brood size seems to be adjusted to parental provisioning abilities.
Adults may eat the excrement of hatchlings when they are younger than 5 days (145), but in general they carry fecal sacs away from the nest . At the late nestling stage, when adults cease entering nest, the excrement accumulates, but nestlings cling to the interior walls of the cavity above the compost. Fecal sacs have a thick, white, resilient outer coating and are solicited from a nestling by the adult biting at the heels or fleshy tail protuberance (145). Both sexes remove fecal sacs, but the male usually removes more (133, 244). Based on videotaping at 96 nests, males removed fecal sacs during 63% of feeding trips at a rate of 1.04 ± 0.05 SD trips/h, whereas females removed fecal sacs after 42% of feeding trips at a rate of 0.7 ± 0.05 trips/h (244). Fecal sacs are carried from the nest and deposited at a distance of 100+ m. Widowed males decreased the rate of fecal sac removal in an apparent trade-off to invest more time in foraging for the brood (187).
Parents typically remove dead small nestlings but may leave carcasses of older nestlings (< approximately 12 d) in the cavity (KLW). At early stages (day 1 to day 10, post-hatching), parents may peck at the cavity interior to add some fresh chips to the bottom of the cavity.
Carrying of Eggs or Young
Not known in the context of parental care. There are some anecdotal reports of flickers carrying eggs out of cavities but these appear to happen after nest disturbance (e.g. 245, 246) and are probably attempts to clear the nest for a subsequent nesting attempt.
Brood Parasitism by Other Species
Rarely, Northern Flickers incubate eggs of other species (e.g., Hooded Merganser (Lophodytes cucullatus), European Starling (Sturnus vulgaris), Mountain Bluebird (Sialia currucoides)) among their own eggs (247), but this probably results from limited availability of nest sites and cavity take-overs by the flicker rather than intentional brood parasitism.
Intraspecific (conspecific) brood parasitism does occur (see Egg Laying).
Departure from the Nest
The average age of fledging in Riske Creek was 25 days (range 21‒26; KLW), similar to that observed in Iowa, an average of 25 d (range 24‒27; 145). Nestlings appear to leave in the order they hatch (145) but this needs more study. Fledglings leave the nest abruptly, usually in an initial flight of ≥ 50 m, and appear not to return (KLW). Adults increase the use of Peah and the Abbreviated Long Call just before fledging; frequency of feeding decreases, and nestlings sometimes lose weight; hunger and calling of adults probably motivate fledglings to leave nest (133, 171). Nest disturbance or threat by a predator when nestlings are nearly ready to fledge can promote flight from the nest.
Fledglings are similar to adults in mass, but their tails and wings are shorter, and they have duller and looser plumage.
Association with Parents or Other Young
During the first week after fledging, parents usually left their young at a certain location (often clinging to the side of a tree) and returned periodically to feed them (191). To initiate feeding, parents gave a series of soft Wicka calls that signaled the fledglings to move to the parent to receive a regurgitated meal. Between 7–10 days post-fledging, the offspring began to follow their parents to foraging sites where they either watched their parents or foraged for themselves. Based on the radio-tracking of 25 pairs at Riske Creek, British Columbia, males continued to feed fledglings on average for 16 days after they left the nest (range 11–22 days), significantly longer than females which fed fledglings on average for 12 days (range 0–21 days; 191). Parents did not usually split the brood, but in three of 25 cases, certain offspring were only seen with one of the parents. Males spent more time closer to fledglings (within 50 m of them) than females (191). After the first week, fledglings acted aggressively to their parents when their begging attempts were sometimes ignored. After about 5–30 minutes of begging without being fed, fledglings would start foraging themselves. Similarly, Sherman (145) reported a fledgling in Iowa being denied food by its mother 22 days after fledging.
The monitoring of 26 family groups in the post-fledging period at Riske Creek showed that between 0–4 days post-fledging, the young birds stayed near their siblings, usually within 50 m of each other, and did not usually move more than 150 m during observation periods lasting one hour (248). Within the first 4 days after leaving the nest, the family was located a median distance of 145 m (range 26–1,074) from the nest site. By 18 days post-fledging, the young had moved an average distance of 592 m (range 64–1,325) from the nest site. Fledglings moved greater distances from nest sites with less forest cover, and their survival rate was positively correlated with the amount of canopy cover which likely provided protection from avian predators (248).
Ability to Get Around, Feed, and Care for Self
Fledglings can fly a considerable distance upon first flight from the nest, although initial perching attempts on branches may be somewhat awkward (KLW). A few fledglings attempted to forage on the ground for themselves as early as 2 days after leaving the nest, but depend on supplemental feeding from their parents for 2–3 weeks (see above).
Little is known of the juvenile life history from Preformative molt until young return to breed as 1-year-olds. In migratory populations, first year birds also migrate, but it is not known whether they do so in family groups.