Breeding

Phenology

Pair Formation

For all populations described so far, major peak in fall, during flock formation. Also during winter (where enough winter floaters are available) and in spring; both winter and spring pair formation typically occur in response to mortality. Male and female members of pairs can be understood to mate assortatively according to rank such that the highest-ranking male in a flock is paired with the highest rank female etc. Females do not simply attain the rank of their mate but may establish rank independently of males (Ramsay and Ratcliffe 2003).

NeSt Building

Generally 1-2 weeks before egg-laying (see Nest, below).

First/Later Broods

Figure 4 . Timing depends on location (primarily local climate); local spring weather; local food supply; and probably also, at the individual level, physical condition of the female, with older, higher-ranking females beginning before younger ones (Smith 1991). There can be considerable annual variation in laying date. In New York females began laying 2 weeks earlier if conditions in April were warmer and drier than normal (Odum 1941c). In British Columbia, clutch completion dates varied by nearly 2 weeks over 3 years, and were also earlier in years with warm April temperatures; clutch initiation date from 1994-2001 was influenced by May North Atlantic Oscillation (NAO) values in Ontario (Ramsay and Otter 2007).

Egg dates: Illinois, Apr 20–Jun 11 (17 records); Massachusetts, May 7–Jul 12 (27); Nova Scotia, May 21–Jun 6 (5); Oregon, Apr 13–Jun 30 (57) (Bent 1946); Michigan, Apr. 18–Jul 3 (38, Nickell 1956).

Replacement broods, begun after loss of a first brood, often started within a few days of loss and may have lower clutch sizes and hatching asynchrony (Smith 1991, Ramsay and Otter 2007). Actual second broods (begun after first clutch fledges young) are rare in chickadees; possibly more frequent in low density populations.

Nest Site

In Ontario, cavities are found most often in birch (50%), aspen (14%), and sugar maple (14%; Mennill and Ratcliffe 2004b). In interior British Columbia, most nest cavities are found in aspen (Martin et al. 2004). Nests in species of tree other than birch and aspen are often associated with knot-holes and may have been previously excavated by another species (Mennill and Ratcliffe 2004b). Sites range from ground level to more than 20 m high; most commonly between 1.5 and 7 m (Smith 1991). Nest trees average 20.5 cm (dbh; Ramsay et al. 1999, Martin et al. 2004). Average cavity depth 21 cm (range 10 to 46 cm; Odum 1941a). More likely to use boxes if natural cavities are scarce. Chickadees prefer artificial nest snags to nest boxes, but for both types of artificial nest, use increases if cavity is filled with wood shavings (Cooper and Bonter 2008).

Both sexes participate in excavation. Birds use beaks to remove substrate (usually rotten wood). In British Columbia, 87% of chickadee nests were in excavated cavities while 13% were found in existing holes (natural holes, not excavated by chickadees or previously by other primary excavators; Aitken and Martin 2007). Where available, several sites are excavated before the final choice is made. Since female alone builds the nest inside the cavity, she often selects the site; sometimes the male participates or even leads in site selection (Smith 1974). Carolina Chickadee nests that are closer to the ground and in softer wood are preyed upon more often than higher, more solidly housed nests (Albano 1992). In Black-capped Chickadees, nest height has no influence on nest success (Chrisman and Dhont 1997). For information on predation rates and types of predators, see Behavior: predation (above).

Nest cavity entrance orientation is unrelated to compass direction (Mennill and Ratcliffe 2004b). However, females with extra-pair young that nested in soft substrates had cavity entrances that were oriented toward extra-pair mates. Cavities have directional acoustic properties such that females can better hear males singing in front of the cavity than behind the cavity. Most have side entrances, often on the downward side of a slanting snag or branch; a few (about 15–20%) have top entrances (Smith 1991). Proportion probably varies with local site availability. Nests are placed on average 17 m from territory boundaries and are nearer to territory boundaries than territory centers (Ramsay et al.1999, Mennill and Ratcliffe 2004b). Females with low-ranking partners place their nest near territory boundaries of higher-ranking males, but no relationship has been found between nest placement and extra-pair partner choice.

Nest

Nests built exclusively by females inside cavities excavated by both pair members. Foundation typically of coarse material such as moss; lining of finer material like rabbit fur and deer hair. Often built in 4–5 d; sometimes just 2 d (Odum 1941b) or as long as 2 wk (Bent 1946). Probably varies with cavity size and perhaps also with time within breeding season. Very rarely no nest is constructed within a cavity (Smith 1991). Dimensions vary with cavity size.

Microclimate

No published data on microclimate of nests. Insulative value probably very high; Mayer et al. (1982) found that roosting in an enclosed cavity during the winter reduced radiant heat loss from Carolina Chickadees (Parus carolinensis) by 60%–100%, and eliminated heat loss by convection.

Reuse Of Nest

Rare, except where alternative sites unavailable. When old cavities are reused, clutch size is larger and laying date is earlier (Wiebe et al. 2007). If a nest is lost to predation, typically replacement nest is some distance away (Smith 1991). Distance between nests in subsequent years is usually further than 60 m (Ramsay et al.1999). When reusing an old nest, or using the nest of another species (such as Hairy Woodpecker Picoides villosus) birds will further excavate the bottom of the nest cavity.

Nonbreeding Nests

No evidence that Black-capped Chickadees construct any nonbreeding nests.

Eggs

Shape

Rounded-ovate.

Size

Average dimensions of 50 eggs: 1.52 cm long and 1.22 cm wide (Bent 1946).

Color

Ground color white, marked with fine dots or spots of reddish brown, often concentrated about the larger end.

Surface Texture

Smooth, with little or no gloss.

Egg Laying

Often begun within a day or two of nest completion. Typically 1 per day, laid early in the morning (Odum 1941b, Kluyver 1961). Some nest material may be added during egg laying period (Nickell 1956). Female typically roosts nightly in nest cavity at this time. Parental behavior during egg laying includes some mild mate-guarding, and “courtship” feeding is particularly prominent in response to Broken dee vocalizations. Otter et al. (1998) documented two cases of intraspecific brood parasitism on the basis of genetic evidence. Smith (1989) suggested that this might be a possible strategy for female summer floaters.

Incubation

Exclusively by female. Incubation typically begins when next-to-last egg is laid; earlier in replacement or second clutches (Smith 1991). Females get single brood patch on belly which is fully developed by the end of egg laying. Rarely, partial brood patches found on males (Kluyver 1961); no evidence as yet that males ever sit on eggs. Incubation period usually 12–13 d. Female covers eggs with nest lining material when leaving the nest (Nickell 1956,Kluyver 1961).

Male regularly brings food to incubating female. Often, upon male arrival at the nest, the pair leaves the nest together to forage, before female returns for further incubation. High and low-ranking males feed their mates at the same rate (Otter et al. 1999). Females produce broken-dee vocalizations to elicit male feeding and the rate of calling is hunger dependent, suggesting it is an honest signal and functions similar to begging in nestlings. Females call at a high rate of up to 12-15 vocalizations/min. Subordinate females in low quality habitat signal (presumably hungrier) at a higher rate than dominant females (Otter et al. 2007a).

Average “on” period is about 20–25 min; extremes reported as 6–60 min. Average “off” period is 7–8 min; extremes, 2–23 min. Brewer (1961) reported an average attentiveness of 75%. Females mated to high-ranking males spend more time on the nest than females mated to low-ranking males (Otter et al. 1999). Females spend more time off the nest when ambient temperatures are higher, and increase attentiveness below 14 ºC (Voss et al. 2006).

No information on hardiness of Black-capped Chickadee eggs against temperature stress and/or effects of egg neglect.

Hatching

Preliminary Events And Vocalizations

Eggs pipped from inside by nestling. No pre-hatching vocalizations noted, although Clemmons and Howitz (1990) found nestlings give faint calls the day they hatch.

Shell Breaking And Emergence

No information on time of day of hatching; may occur at any time as with Carolina Chickadees (Brewer 1961). Typically all eggs hatch within 12–30 h; tend to hatch in order they were laid (Odum 1941b). No information on average interval between hatching of eggs.

Parental Assistance And Disposal Of Eggshells

No direct parental assistance reported. Eggshells removed from nest; taken some distance, then either dropped or eaten (Odum 1941b).

Young Birds

Condition At Hatching

Altricial, eyes closed. Mass ± 1 g (Odum 1941b, Kluyver 1961). Naked, except for 6 small patches of pale mouse gray neossoptiles, all on the dorsal surface. Two down tufts located in the superciliary region of the capital tract; two tufts on the humeral tract; one tuft on the cervical and one on the dorsal region of the dorsal or spinal tract. Only 2–12 neossoptiles per tuft; one bird had only 29 down feathers total (Odum 1941b). These persist and are pushed out by, and remain attached to, the juvenal feathers until worn away after the bird leaves the nest. Color of bare parts: skin pinkish orange, bill blackish, legs pinkish gray; corners of mouth bright yellow, mouth lining pinkish, no pattern. Nestlings gape for food on day of hatching; also give faint calls (Clemmons and Howitz 1990).

Growth And Development

Developing contour feathers show as dark specks in dorsal feather tracts within a day or two after hatching; all feather tracts show developing contour feathers by day 4. “Pin-feather” stage reached by day 9; by day 12 the body mostly covered by contour feathers, with bare patches on the body (especially the belly); the remiges are still partly sheathed. By day 15 or 16, bare patches far less noticeable; resemble adults except for mouth corners and shorter tail and wings. Mass increases steadily from about 1 g at hatching (av. 1.13 g, Odum 1941b) to 10–12 g (Odum 1941b; 11.3 g, Kluyver 1961) by day 15. K value for growth curve 0.384 (Ricklefs 1968). Males have a faster growth rate than females, and by day 6 males are significantly heavier than females (Boon 2002). Shivering appears about day 4, well developed by day 9, but not effective in thermoregulation until day 12, when the nestlings have sufficient contour feathers to retain body heat (Odum 1941b).

Nestlings move about actively within the nest at all ages, especially when hungry. In crowded nests recently-fed nestlings settle near bottom, with more hungry ones working their way to the top. Stretching and preening appear about day 9–12; birds come to the nest entrance and look out often by day 13 or 14, and whirr their wings repeatedly within 1–2 day of leaving the nest. Calls gradually change from faint peeps to several noisy vocalizations, all associated with feeding; the Begging Dee call typically not given until the birds have left the nest.

Parental Care

Brooding

Only females brood. Rhythmic; same pattern as incubation first few days after hatch, with about 20–25 min spent on the nest for every 8–10 min spent off. Gradually lessens; does not completely stop until about 12 d post-hatch, when young can thermoregulate. Male brings most of food during the first 12 d; he feeds the brooding female and also brings food for the nestlings.

Feeding

Young fed from day of hatching through to juvenile dispersal, 2–4 wk after the young leave the nest. Both parents feed the young. Male brings virtually all of the food right after hatching, when the nestlings need brooding; by day 8 the female brings about 30% of the food; by day 13 the parents bring equal amounts. Parents carry food to the nest in their beaks. Females feed the young directly; males either do likewise or, when the female is brooding, give food to her to feed the young. Parents produce squawk calls to stimulate gaping during feeding (Clemmons 1995a). Nestlings gape to inappropriate stimuli on day 0-1 and the squawk may function to couple gaping with food presentation. Preference for gaping in response to squawks emerges on day 2-3 and increases until day 11-13 when gaping occurs only in response to squawks (Clemmons 1995b).

Little detailed information on food brought to young; mostly animal matter, particularly caterpillars. Nickell (1956) reported that parent Black-capped Chickadees in Michigan brought nestlings mostly spruce bud-worm (Archips fumiferana) and spring canker-worm (Paleacrita vernata) caterpillars, but gave no proportions. Kluyver (1961), working in Massachusetts, tried to constrict nestlings’ throats to gather samples; most such nestlings refused to beg, but he did manage to get a sample of 65 items this way. This included 35 caterpillars (13 large and 22 small), 11 spiders, 6 small unidentified larvae, 4 small red larvae, 6 termites, 1 white butterfly or moth, 1 pupa, and 1 fly. Since the caterpillars weighed so much more than the other items, by far the bulk of this sample was caterpillars. Kluyver also found that the average weight of food brought per visit varied markedly from nest to nest.

Feeding rates (number of feedings/young/h) increase steadily with nestling age; Kluyver (1961) suggested that rate of feeding may be largely regulated by intensity of nestlings’ begging. Other factors include age/experience of adults, and territory quality. High-ranking birds make more trips to the nest than low-ranking birds in poor-quality habitat, however, there is no effect of rank in high-quality habitat (van Oort et al. 2007). Just before young leave the nest, feeding rates often dip slightly (Kluyver 1961, Smith 1976), although not enough to lower the nestlings’ weights.

Nest Defense

Potential predator near nest often elicits the Nest-site Distraction Display from parent, which leans forward, spreads its tail, and slowly raises and lowers its fully-extended wings, while swaying from side to side. Often given by both parents simultaneously. May be accompanied by a loud vocalization, e.g., Modified High Zees (Long 1982).

Nest Sanitation

Nestling fecal sacs, covered with mucous and produced right after feeding, get carried away from nest by both parents. Parents often eat fecal sacs produced within a few days of hatching.

Infestations by parasites are rare, at least in most natural woodland areas, probably because Black-capped Chickadees seldom reuse a nest site. May be higher in areas where nest sites are limited.

Cooperative Breeding

Not observed.

Brood Parasitism

Rare, as with most hole-nesting species, especially those considerably smaller than Brown-headed Cowbirds (Smith 1991). Intraspecific brood parasitism was documented in Ontario, but is rare (Otter et al. 1998).

Fledgling Stage

Young leave undisturbed nests when about 16 d old; if disturbed, as early as 12 d. A parent sometimes accompanies a young bird on its first flight. Most broods leave the nest during the morning; all members of a brood typically within 1–2 h of each other. After a few young leave, parents may perch near the nest and give faint fee-bees, and/or carry food to the nest, then take it away again, possibly to get the rest of the brood to leave.

Once young leave nest, they do not return there to roost but gather in groups and move away, evidently following parents’ lead (Odum 1941b). Young give frequent begging dees and are fed by both parents. Birds leaving undisturbed nests are well developed; most can fly well. Odum (1941b) reported that all members of a brood he saw fledge one morning roosted several hundred meters away from the nest site their first night. At this stage young birds weigh about as much as adults (Kluyver 1961), although doubtless some mass, particularly breast muscle, is added soon after fledging. Yellow corners of mouth are soon lost; wings and tails grow rapidly so that within 7–10 d of leaving the nest, young become difficult to distinguish from adults.

Young stay with adults for 3–4 wk (occasionally as little as 2) after leaving the nest. To begin with, parents provide all of their food, although young usually catch first food items within a week of leaving the nest, both in the wild (Odum 1941b) and in captivity (Smith 1991). Gradually young catch more and more on their own, until they are ready to disperse.

Immature Stage

Juvenile dispersal happens suddenly: one day the whole brood is with both parents; the next, the young scatter and move some distance away. Dispersal evidently not triggered either by increased parental aggression (Weise and Meyer 1979) or by decreased food provision (Smith 1991). In some European tits, subordinate birds move farther away than dominants; needs study in chickadees. Dispersal in chickadees is essentially random in direction; Weise and Meyer (1979) found no significant difference in distance between males and females, although males may settle closer; more research is needed. Female chickadees are more discriminating than males when dispersing such that female settlement follows an ideal-despotic distribution (first arrivals establish themselves in richer habitat, and then defend resources by setting up territories in order to force out later arrivals) while male settlement follows a non-ideal distribution (van Oort and Otter 2005).

Dispersed immatures soon settle into newly forming winter flocks, sometimes having associated with temporary aggregation of other juveniles for a few days or (rarely) weeks before settling. Flocks are thus made up of local breeders (≥ 1 y old) and unrelated young that have hatched some distance away. Most young chickadees become regular members of one flock. Winter populations may contain both regular flock members, which typically spend the whole winter in a single flock, and also winter floaters—birds whose home range includes that of 3 to 5 flocks, with an established position in the dominance hierarchy of each one. Under suitable conditions, a high-ranking bird that disappears from a flock may be replaced by a floater, which assumes the rank, and pairs with the mate of the vanished bird. Such replacements evidently occur only where floater density is high. In years of relatively poor local food supply, may be forced to move away, in a more-or-less southward direction, as part of an irruption.