Plumages, Molts, and Structure

Northern Cardinal has 9 functional primaries (numbered distally, p1 to p9), 9 secondaries (numbered proximally, s1 to s9, and including 3 tertials, s7–s9 in passerines), and 12 rectrices (numbered distally, r1 to r6, on each side of the tail). Geographic variation in appearance is moderate. The following plumage descriptions pertain to the northern subspecies C. c. cardinalis; see Systematics: Geographic Variation for variation in 17 other recognized subspecies in the southern United States, Mexico, and Central America.

Sexes are similar in Juvenile Plumage but differ in subsequent plumages; definitive appearance assumed by Second Basic Plumage, although some birds attain definitive-like appearance in Formative Plumage. The following descriptions are based primarily on specimen examination and detailed plumage descriptions from Ridgway (61 Ridgway, R. (1901). The birds of North and Middle America. Part 1. United States National Museum Bulletin 50. Close ), Bent (62 Bent, A. C. (1968). Life histories of North American cardinals, grosbeaks, towhees, finches, sparrows, and allies (Part 1). United States National Museum Bulletin 237. Close ), Oberholser (63 Oberholser, H. C. (1974). The Bird Life of Texas. University of Texas Press, Austin, Texas, USA. Close ), and Yen (64 Yen, C. W. (1989). A plumage study of the Cardinal (Cardinalis cardinalis cardinalis) of western Pennsylvania. Bulletin of the National Museum of Natural Sciences (Taiwan) 1: 11–21. Close ); see Scott (46 Scott, D. M. (1967). Postjuvenal molt and determination of age of the Cardinal. Bird-Banding 38: 37–51. Close ), Wiseman (65 Wiseman, A. J. (1968). Ageing cardinals by juvenal secondaries and secondary coverts. Inland Bird Banding News 40: 172–173. Close , 47 Wiseman, A. J. (1977). Interrelation of variables in postjuvenal molt of Cardinals. Bird-Banding 48:206–223. Close ) and Pyle (66 Pyle, P. (1997). Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. Close ) for age-related criteria.

Natal Down

Present March–August; wide spread in timing here and in other stages linked to a long breeding season with multiple nestings. Hatchlings partially covered with gray down, 6–11 mm long, on coronal, occipital, middorsal, pelvic, scapular, femoral, and greater secondary-covert and median secondary-covert regions at hatching (67 Kinser, G. W. (1973). Ecology and behavior of the Cardinal, Richmondena cardinalis (L), in southern Indiana. Ph.D. dissertation, Indiana University, Bloomington, IN, USA. Close ).

Juvenile (First Basic) Plumage

Present primarily in April–August. Similar to Definitive Basic female but duller, crest and flight-feathers more brownish, with less red plumage apparent on the body; juvenile body feathers (especially undertail coverts) filamentous due to lower barb density. Juvenile outer primaries and rectrices narrower and more tapered at tips than in later plumages (cf. 46 Scott, D. M. (1967). Postjuvenal molt and determination of age of the Cardinal. Bird-Banding 38: 37–51. Close , 47 Wiseman, A. J. (1977). Interrelation of variables in postjuvenal molt of Cardinals. Bird-Banding 48:206–223. Close , 66 Pyle, P. (1997). Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. Close ). Wiseman (47 Wiseman, A. J. (1977). Interrelation of variables in postjuvenal molt of Cardinals. Bird-Banding 48:206–223. Close ) cautioned that damaged feathers in adults are also replaced by more pointed feathers. Sexes similar.

Auxiliary Formative Plumage

The "Supplemental Plumage" of Thompson and Leu (48 Thompson, C. W., and M. Leu (1994). Determining homology of molts and plumages to address evolutionary questions: A rejoinder regarding emberizid finches. Condor 96:769–782. Close ); see revisions by Howell et al. (68 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: a review of molt and plumage homologies. Condor 105:635–653. Close ). Present primarily in June–September. Similar to Juvenile Plumage but variable number of body feathers replaced, the new feathers reported to be brown like juvenile feathers, although in males some body feathers may be red; more study needed on this particular molt stage and resultant plumage.

Formative Plumage

Analogous to "First Basic" or "Basic I" plumage of Humphrey and Parkes (69 Humphrey, P. S., and K. C. Parkes (1959). An approach to the study of molts and plumages. The Auk 76(1):1–31. Close ) and some subsequent authors; see revision by Howell et al. (68 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: a review of molt and plumage homologies. Condor 105:635–653. Close ). Present in first-year birds, primarily from September to the following August. Similar to Definitive Basic Plumage, however, in most but not all birds, molt limits occur variably among the wing feathers. Retained juvenile feathers appear duller or paler (faded) or tinged brown, and narrower and more tapered (outer primaries and rectrices), contrasting with replaced fresher and better-quality formative feathers, which are brighter red, especially in males. Molt limits can occur among upperwing coverts, with, e.g., inner greater coverts replaced, contrasting with retained juvenile outer greater coverts and primary coverts; or, molt limits can occur among primaries, primary coverts, and secondaries with replacement of just a portion of these feathers in typical molt sequence. Last feathers replaced are the outer primaries and primary coverts, and secondaries among s5–s6. Some birds replace all primaries and primary coverts and retain only 1 juvenile secondary (often s6). Similarly, rectrices can be completely retained, typically in those birds that do not molt any remiges, to completely replaced, typically in birds that have replaced at least 4–6 inner primaries (P. Pyle, personal communication). An unknown proportion of hatch-year birds can replace all body and flight-feathers in the Preformative Molt, becoming indistinguishable from adults in Definitive Basic Plumage (48 Thompson, C. W., and M. Leu (1994). Determining homology of molts and plumages to address evolutionary questions: A rejoinder regarding emberizid finches. Condor 96:769–782. Close ); it is possible that more birds in southern populations replace all juvenile feathers than do birds in northern populations (70 Pyle, P. (1997). Molt limits in North American passerines. North American Bird Bander 22:49–89. Close , 66 Pyle, P. (1997). Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. Close ). However, most individuals in Formative Plumage have molt limits or contrasts among feathers of the upperwing and tail, and retained worn, narrow, or brownish-tinged flight feathers contrasting with newly molted uniformly red to reddish flight feathers (66 Pyle, P. (1997). Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. Close ).

Definitive Basic Plumage

Present in birds in their second autumn and beyond, primarily from September to the following August. Newly molted contour feathers of back and neck tipped with gray; by late winter or early spring, feather-tips are worn off and plumage attains maximum coloration (62 Bent, A. C. (1968). Life histories of North American cardinals, grosbeaks, towhees, finches, sparrows, and allies (Part 1). United States National Museum Bulletin 237. Close , JMJ).

Female. Upperparts plain grayish olive or buffy grayish; head with conspicuous crest, variably red to tipped red. Face mask variable: large and dark, much like that of male, to dull grayish, smaller and less distinct than that of male; sometimes nearly white on throat. Upperwing greater coverts and secondaries duller red than primaries and rectrices; duller than those of male. Underparts pale fulvous or buffy, but some individuals can show nearly white coloration on abdomen. Plumage often with small numbers of red or red-tinged feathers above eye, and among auriculars and feathers of the upper breast and flanks. Underwing secondary coverts light orange to light red ; in Ohio (29 Linville, S. U., R. Breitwisch, and A. J. Schilling (1998). Plumage brightness as an indicator of parental care in male and female Northern Cardinals. Animal Behaviour 55: 119–127. Close ), female underwing coverts ranged from 8.75 R 4/16 to 10 R 6/13 on Munsell Color Scale. In Mississippi, reflectance measures of underwing plumage from color reflectance spectrometer peak in the 600–700 nm range (JMJ).

Male. Plumage primarily vermilion red, with black face mask that surrounds bill, extends back to eye, and covers chin and throat. Head with conspicuous crest. Red brightest on auricular region, cheeks, and breast. Upperwing greater coverts and secondaries duller red than primaries and rectrices. Contour feathers of back and neck have olive-gray (Munsell 7.8 Y 5.92/2.0) margins that wear away by early spring; tertials and rectrices may also have olive-grayish margins, and flanks include grayish feathers. Rump and uppertail coverts not distinctly lighter in color than back, crest duller red than breast. Underwing secondary coverts as in female. In Ohio, male red breast color ranged from 7.5 R 4/16 to 8.75 R 5/16 on the Munsell Color Scale (29 Linville, S. U., R. Breitwisch, and A. J. Schilling (1998). Plumage brightness as an indicator of parental care in male and female Northern Cardinals. Animal Behaviour 55: 119–127. Close ). In Mississippi, highest reflectance measures of red upper-breast plumage from color reflectance spectrometer data peak in the 620–750 nm range (JMJ).

Individuals in Definitive Basic Plumage are separated from most individuals in Formative Plumage by lack of molt limits or contrasts among feathers of the upperwing coverts and among flight feathers of the wing and tail (see Formative Plumage). Rather, the definitive basic upperwing coverts and flight feathers of the wing and tail are uniformly red to reddish, without contrasting worn, narrow, or brownish-tinged feathers (66 Pyle, P. (1997). Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. Close ). After complete Preformative Molt, birds in Formative plumage are usually indistinguishable from Definitive Basic Plumage adults by plumage.

Proximate Control of Coloration

Carotenoid pigments are important components in the plumage of many birds. Red and orange colors in Northern Cardinal result from deposition of carotenoid pigments: canthaxanthin, astaxanthin, phoenicoxanthin, α-doradexanthin, e, e-carotene-3,3´-dione, adonirubin, and 3 unidentified carotenoid pigments (71 Hudon, J. (1990). Unusual carotenoid use by the Western Tanager (Piranga ludoviciana) and its evolutionary implications. Canadian Journal of Zoology 69:2311–2320. Close , 72 McGraw, K. J., G. E. Hill, and R. S. Parker (2003). Carotenoid pigments in a mutant Cardinal: implications for the genetic and enzymatic control mechanisms of carotenoid metabolism in birds. Condor 105:587–592. Close ). A male cardinal showing yellow coloration over the whole body had no red carotenoid pigments identified in its plumage, only yellow carotenoid pigments: lutein, 3’-dehydrolutein, canary-xanthophyll B, and canary-xanthophyll A (72 McGraw, K. J., G. E. Hill, and R. S. Parker (2003). Carotenoid pigments in a mutant Cardinal: implications for the genetic and enzymatic control mechanisms of carotenoid metabolism in birds. Condor 105:587–592. Close ). McGraw et al. (72 McGraw, K. J., G. E. Hill, and R. S. Parker (2003). Carotenoid pigments in a mutant Cardinal: implications for the genetic and enzymatic control mechanisms of carotenoid metabolism in birds. Condor 105:587–592. Close ) suggested the individual might have lacked enzymes necessary for conversion of yellow carotenoids to red forms. McGraw et al. (73 McGraw, K. J., G. E. Hill, R. Stradi, and R. S. Parker (2001). The influence of carotenoid acquisition and utilization on the maintenance of species-typical plumage pigmentation in male American Goldfinches (Carduelis tristis) and Northern Cardinals (Cardinalis cardinalis). Physiological and Biochemical Zoology 74(6):843–852. Close ) fed captive male cardinals a seed diet that they determined contained only the carotenoids lutein, zeaxanthin, β-cryptoxanthin and β-carotene. Carotenoids in the feathers grown by these males included α-doradexanthin, astaxanthin, canthaxanthin, and adonirubin (73 McGraw, K. J., G. E. Hill, R. Stradi, and R. S. Parker (2001). The influence of carotenoid acquisition and utilization on the maintenance of species-typical plumage pigmentation in male American Goldfinches (Carduelis tristis) and Northern Cardinals (Cardinalis cardinalis). Physiological and Biochemical Zoology 74(6):843–852. Close ). The authors noted that breast feathers grown by males in captivity were less densely pigmented than those of wild caught males (73 McGraw, K. J., G. E. Hill, R. Stradi, and R. S. Parker (2001). The influence of carotenoid acquisition and utilization on the maintenance of species-typical plumage pigmentation in male American Goldfinches (Carduelis tristis) and Northern Cardinals (Cardinalis cardinalis). Physiological and Biochemical Zoology 74(6):843–852. Close , 74 McGraw, K. J., and G. E. Hill (2001). Carotenoid access and intraspecific variation in plumage pigmentation in male American Goldfinches (Carduelis tristis) and Northern Cardinals (Cardinals cardinalis). Functional Ecology 15(6):732–739. Close ). This work shows that cardinals are able to enzymatically alter carotenoids obtained from their diet prior to deposition into feathers; however, the underlying physiological and enzymatic contributions to the range of differences in individual coloration reported among adults of both sexes (e.g., 75 Linville, S. U. (1997). Sexual selection and plumage ornamentation in a socially monogamous passerine, the Northern Cardinal (Cardinalis cardinalis). Ph.D. dissertation, University of Dayton, Dayton, OH, USA. Close , 76 Wolfenbarger, L. L. (1999). Red coloration of male northern cardinals correlates with mate quality and territory quality. Behavioral Ecology 10:80–90. Close , 77 Wolfenbarger, L. L. (1999). Is red coloration of male Northern Cardinals beneficial during the nonbreeding season?: a test of status signaling. Condor 101(3):655–663. Close , 78 Wolfenbarger, L. L. (1999). Female mate choice in Northern Cardinals: Is there a preference for redder males? Wilson Bulletin 111(1):76–83. Close ) remain to be studied.

The black face mask in both sexes is melanin-based coloration, a pigment type that is independent of diet. In a Mississippi population, male and female testosterone levels were measured through the molt period in captive individuals and it was found that females with higher average testosterone throughout the molt period grew darker face mask feathers (C. P. Winters and JMJ, unpublished data). This association did not hold for males.

Assessment of carotenoid-based plumage for ultraviolet reflectance has not found significant ultraviolet signatures in either sex (76 Wolfenbarger, L. L. (1999). Red coloration of male northern cardinals correlates with mate quality and territory quality. Behavioral Ecology 10:80–90. Close ); melanin-based plumage needs to be assessed for ultraviolet signatures.

Aberrant Plumages

Individuals having a mix of male and female plumage infrequently reported from across the species range. See for an example of mixed plumage; the pictured individual, apparently female, was initially thought to be male, but was captured when flushed from a nest where it appeared to be incubating eggs. This bird had an incubation patch, and the nest produced 3 fledglings, fed by both this individual and its social mate, a male with definitive male coloration. Older females of many bird species can obtain male-like plumage as androgen levels decline with age resulting in greater hormonal effects of testosterone (79 Lindsay, W. R., D. G. Barron, M. S. Webster, and H. Schwabi (2016). Testosterone activates sexual dimorphism including male-typical carotenoid but not melanin plumage pigmentation in a female bird. Journal of Experimental Biology 219: 3091–3099. Close ). Other individuals, potentially bilateral gynandromorphs, have been reported with red on one side and gray-olive on the other (80 Laskey, A. R. (1969). Bilaterial gynandrism in a Cardinal and a Rufous-sided Towhee. Auk 86: 760. Close , 81 Peer, B. D., and R. W. Motz (2014). Observations of a bilateral gynandromorph Northern Cardinal (Cardinalis cardinalis). Wilson Journal of Ornithology 126: 778–781. Close , 82 Jones, A. W., and H. T. Bartlett (2017). A bilateral gynandromorph Northern Cardinal from South Bass Island. Ohio Biological Survey Notes 7: 14–16. Close , 83 Tumlison, R., D. B. Sasse, H. W. Robison, M. B. Connior, C. T. McCallister, K. Jobe, and M. Anderson (2018). Vertebrate natural history notes from Arkansas, 2018. Journal of the Arkansas Academy of Science 72 (Article 7). Close ) ; development and fertility of potential gynandromorphs needs additional assessment in this and other avian species. Also reported are leucistic and partially leucistic individuals (e.g., 84 Hartman, F. E. (1968). White-headed Cardinal. Bird-Banding 39: 57. Close , SUL) , a non-phaeomelanic individual , non-eumelanic individuals , completely yellow individuals (72 McGraw, K. J., G. E. Hill, and R. S. Parker (2003). Carotenoid pigments in a mutant Cardinal: implications for the genetic and enzymatic control mechanisms of carotenoid metabolism in birds. Condor 105:587–592. Close , 85 Winstead, N. A. (2017). Aberrantly-colored yellow Northern Cardinals. Mississippi Kite 47: 40–43. Close , also in Alabama and Georgia in 2018, and Florida in 2019) , a dilute individual , and a melanistic male with a black head (86 Brooks, M. (1934). A melanistic Cardinal at French Creek. Redstart 1: 1–2. Close ). One rare instance of a banded female that obtained male plumage color in year 5 among 8 years of recapture; she returned to female color in year 6 (87 Baumgartner, A. M. (1986). Sex-reversal in banded Cardinal. North American Bird Bander 12: 76. Close ).

Molt and plumage terminology follows Humphrey and Parkes (69 Humphrey, P. S., and K. C. Parkes (1959). An approach to the study of molts and plumages. The Auk 76(1):1–31. Close ), as modified by Howell et al. (68 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: a review of molt and plumage homologies. Condor 105:635–653. Close , 88 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2004). The first basic problem revisited: reply to commentaries on Howell et al. (2003). Condor 106:206–210. Close ). Northern Cardinal exhibits a Complex Basic Strategy (cf. 68 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: a review of molt and plumage homologies. Condor 105:635–653. Close , 89 Howell, S. N. G. (2010). Peterson Reference Guide to Molt in North American Birds. Houghton Mifflin Harcourt, Boston, Massachusetts, USA. Close ), including complete prebasic molts, an absent-to-limited auxiliary preformative molt (90 Sutton, G. M. (1935). The juvenal plumage and postjuvenal molt in several species of Michigan sparrows. Cranbrook Institute of Science Bulletin 3. Bloomfield Hills, MI, USA. Close , 48 Thompson, C. W., and M. Leu (1994). Determining homology of molts and plumages to address evolutionary questions: A rejoinder regarding emberizid finches. Condor 96:769–782. Close ), and a partial-to-complete preformative molt but no prealternate molts (91 Stone, W. (1896). The molting of birds with special reference to the plumages of smaller land birds of eastern North America. Proceedings of the Academy of Natural Sciences of Philadelphia 43:108–164. Close , 92 Dwight, J., Jr. (1900). The sequence of plumages and moults of the passerine birds of New York. Annals of the New York Academy of Sciences 13:73–360. Close , 46 Scott, D. M. (1967). Postjuvenal molt and determination of age of the Cardinal. Bird-Banding 38: 37–51. Close , 93 Blake, C. H. (1971). Primary molt in juvenile Cardinals. Bird-Banding 42: 269–274. Close , 94 Reese, J. G. (1975). Fall remix and rectrix molt in the Cardinal. Bird-Banding 46: 305–310. Close , 63 Oberholser, H. C. (1974). The Bird Life of Texas. University of Texas Press, Austin, Texas, USA. Close , 66 Pyle, P. (1997). Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. Close , 95 Pyle, P. (1997). Molt limits in North American passerines. North American Bird Bander 22:49–89. Close ; Figure 1). During molt, patches of old feathers may remain loosely attached.

Geographic variation in average timing and extent of molts likely occurs with latitude of breeding through Mexico and Central America, as a response to variation in environmental constraints, day-length regimes, and breeding seasonality; the Preformative Molt may be more extensive within southern United States populations than in northern populations (66 Pyle, P. (1997). Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. Close , 95 Pyle, P. (1997). Molt limits in North American passerines. North American Bird Bander 22:49–89. Close ), though confirmation needed.

Prejuvenile (First Prebasic) Molt

Complete, primarily April–July, in and near the nest. From Kinser (67 Kinser, G. W. (1973). Ecology and behavior of the Cardinal, Richmondena cardinalis (L), in southern Indiana. Ph.D. dissertation, Indiana University, Bloomington, IN, USA. Close ): Tips of primary quills emerge on day 1. Ventral tract evident on day 2 as white lines along sides of abdomen. Ventral cervical and upper abdominal regions, and femoral and humeral tracts, are apparent on day 3. Upperwing greater and median secondary coverts, crural tract, and occipital region visible on day 4. All feathers completely sheathed on day 5, and begin to break open on day 6. By day 7, primaries are 35 mm long and partly sheathed; free from sheaths by day 8. From Wiseman (47 Wiseman, A. J. (1977). Interrelation of variables in postjuvenal molt of Cardinals. Bird-Banding 48:206–223. Close ): Remiges fully formed in 4 weeks; rectrices erupt about day 7 and mature in 6 weeks; contour feathers develop in irregular patterns within each tract.

Auxiliary Preformative Molt

"Presupplemental Molt" of Thompson and Leu (48 Thompson, C. W., and M. Leu (1994). Determining homology of molts and plumages to address evolutionary questions: A rejoinder regarding emberizid finches. Condor 96:769–782. Close ); see revisions by Howell et al. (68 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: a review of molt and plumage homologies. Condor 105:635–653. Close ). Limited or partial, likely sometimes absent altogether, primarily May–September. This molt first described in Northern Cardinal and some sparrows by Sutton (90 Sutton, G. M. (1935). The juvenal plumage and postjuvenal molt in several species of Michigan sparrows. Cranbrook Institute of Science Bulletin 3. Bloomfield Hills, MI, USA. Close ). On the basis of > 200 museum skins from across the United States (C. Thompson, personal communication): While in the nest or soon after fledging, all or most of body plumage is replaced except for some upperwing secondary coverts; completed within 2 weeks. Molt begins late May to late September and finishes mid-June to early October. Molt likely can be absent in some birds that fledge late, juvenile feathers being directly replaced by formative feathers (P. Pyle, personal communication). Further study is needed on this molt in the Northern Cardinal and in birds in general, as it can be difficult to trace each follicle for activation once or twice during the post-fledging period.

Preformative Molt

"First Prebasic" or "Prebasic I" molt of Humphrey and Parkes (69 Humphrey, P. S., and K. C. Parkes (1959). An approach to the study of molts and plumages. The Auk 76(1):1–31. Close ) and some subsequent authors; see revision by Howell et al. (68 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: a review of molt and plumage homologies. Condor 105:635–653. Close ). Partial to complete, primarily June–November. Timing and completion of Preformative Molt is variable. Birds hatching in May experience a greater temporal gap between Auxiliary Preformative and Preformative Molt; later-hatching individuals maintain shorter gaps, until those hatching in July have no temporal gap or may skip Auxiliary Preformative molt. Birds hatching after July undergo partial molt; August hatchlings retain all rectrices and some secondaries, September hatchlings replace only a few flight-feathers (46 Scott, D. M. (1967). Postjuvenal molt and determination of age of the Cardinal. Bird-Banding 38: 37–51. Close , 93 Blake, C. H. (1971). Primary molt in juvenile Cardinals. Bird-Banding 42: 269–274. Close , 94 Reese, J. G. (1975). Fall remix and rectrix molt in the Cardinal. Bird-Banding 46: 305–310. Close ). Sequence of flight-feather replacement as described under Definitive Prebasic Molt. Of 196 juveniles from Ohio and Kentucky, 58% completed molt of all feathers, 23% retained some rectrices, 12% retained all rectrices and some secondaries, and 7% retained all or most flight-feathers (94 Reese, J. G. (1975). Fall remix and rectrix molt in the Cardinal. Bird-Banding 46: 305–310. Close ). In a sample of museum skins (n = 80) from across the United States, 79% replaced all primaries, 56% all rectrices, and 19% all secondaries (C. Thompson, personal communication). By winter, birds with complete molt are usually indistinguishable from adults (48 Thompson, C. W., and M. Leu (1994). Determining homology of molts and plumages to address evolutionary questions: A rejoinder regarding emberizid finches. Condor 96:769–782. Close ).

Definitive Prebasic Molt

Complete molt of adults, primarily July–October, on or near breeding territories. Northern Cardinals show an unusually low proportion of breeding birds captured molting at MAPS stations (96 Pyle, P., J. F. Saracco, and D. F. DeSante (2018). Evidence of widespread movements from breeding to molting grounds by North American landbirds. Auk: Ornithological Advances 135:506–520. Close ). Low capture rates of molting cardinals could be due to the reclusive behavior of molting cardinals (SLH, unpublished data, southern Wisconsin population); Pyle et al. (96 Pyle, P., J. F. Saracco, and D. F. DeSante (2018). Evidence of widespread movements from breeding to molting grounds by North American landbirds. Auk: Ornithological Advances 135:506–520. Close ) suggested the alternate hypothesis that cardinals might disperse from breeding territories for the molting period, but we have found no direct evidence for this in the populations we have studied (SLH, JMJ). In Maryland, the prebasic molt of remiges is completed in most birds during October and a few in early November (94 Reese, J. G. (1975). Fall remix and rectrix molt in the Cardinal. Bird-Banding 46: 305–310. Close ). Induced rectrix growth (feather removed and replacement feather growth rate assessed by growth bars) was influenced by ambient temperature as well as seasonal cues in adults (97 Grubb, T. C., T. A. White, and A. J. Wiseman (1991). Ptilochronology: Induced feather growth in Northern Cardinals varies with age, sex, ambient temperature and daylength. Wilson Bulletin 103: 435–445. Close ). Growth bars visible in rectrices at angle of 77° to proximal rachis (98 Wood, H. B. (1950). Growth bars in feathers. Auk 67: 486–491. Close ); growth bar width (an estimate of feather growth rate) on tail feathers not found to covary with plumage color in either sex (99 Jawor, J. M. (2002). Multiple ornaments and sexual selection in a socially monogamous passerine, the Northern Cardinal (Cardinalis cardinalis). Ph.D. dissertation, University of Southern Mississippi, Hattiesburg, MS, USA. Close ).

Primaries replaced distally (p1 to p9), secondaries replaced proximally from s1, and proximally and distally from the central tertial (s8), and rectrices replaced distally (r1 to r6) on each side of tail, with some variation in sequence possible. Primarily from Wiseman (47 Wiseman, A. J. (1977). Interrelation of variables in postjuvenal molt of Cardinals. Bird-Banding 48:206–223. Close ): Molt begins in three general regions: (1) all median secondary coverts, (2) small number of feathers in anterior scapular region, and (3) feathers in middle rows of ventral tract on upper breast; head and body feathers molt in irregular patterns and numbers, dorsal feathers first, lateral and ventral feathers later ( ). P1 drops a few days after body molt begins, followed by other primaries at weekly intervals in serial order. Loss of s1, s8, and r1 usually associated with growth of p4; s1 may drop before p4 or it may not drop until p4 is fully grown and p5 is partially grown (C. Thompson, personal communication). S1–s6 replaced in sequential order, proximally; tertials usually molt in order s8-s9-s7 (rarely s7 may drop before s9) and grow rapidly, becoming fully developed before s1–s3 are dropped. Rectrices are replaced in order, distally and rapidly, and are completed before primaries; r5 and r6 are completed last.

Bill and Gape

Gape of nestlings is red-orange; the yellow edge on the mandibles is useful in discriminating nestling cardinals from Brown-headed Cowbird (Molothrus ater) nestlings in eastern and central populations (see Breeding: Young Birds: Condition at Hatching). Bill of nestlings and juveniles is gray to black, but gradually becomes orange; dark areas of bill coloration may persist to at least January (JMJ). Laskey (100 Laskey, A. R. (1944). A study of the Cardinal in Tennessee. Wilson Bulletin 56: 27–44. Close : 31) reported that nestling bill changes to adult color in 65–80 days, though some retain a 1 mm dark upper mandible tip for “several months”. Both males and females have orange-red bills as adults.

The orange-red bill, surrounded by the dark face mask, could provide an aposematic warning or reminder of the cardinal's ability to deliver a painful bite (D. Spector, personal communication).

Iris and Facial Skin

Iris is deep brown, sometimes appearing black.

Tarsi and Toes

Medium brown, sometimes pinkish or orangish.

See Systematics and Appendix 1.

Linear Measurements

Males average larger than females in total length, as well as length of wing, tail, and bill, but ranges of values show considerable overlap between the sexes (Appendix 1). Sgueo (101 Sgueo, C. E. (2009). Seasonal acclimatization through physiological changes in Northern Cardinals (Cardinalis cardinalis). M.S. thesis, Miami University, Oxford, OH, USA. Close ) and Sgueo et al. (102 Sgueo, C., M. E. Wells, D. E. Russell, and P. J. Schaeffer (2012). Acclimatization of seasonal energetics in Northern Cardinals (Cardinalis cardinalis) through plasticity of metabolic rates and ceilings. Journal of Experimental Biology 215: 2418–2424. Close ) found no differences in linear measurements (wing chord, tarsus length, tail length, culmen length) in winter and summer individuals in a southwestern Ohio population. No obvious latitudinal trends among subspecies.

Miller et al. (103 Miller, C. R., C. E. Latimer, and B. Zuckerberg (2018). Bill size variation in Northern Cardinals associated with anthropogenic drivers across North America. Ecology and Evolution 8: 4841–4851. Close ) assessed a composite measure of bill size from 605 museum specimens collected over 85 years across the species' range in the United States. They found that males have larger bills than females, though bill sizes of both sexes showed extensive variation, with considerable overlap between sexes. For information on environmental correlates of bill size, see Systematics: Geographic Variation.

Mass

Mass varies throughout year; highest values October–April in Ohio, October–February in Tennessee (maximum in January), and February in Indiana (102 Sgueo, C., M. E. Wells, D. E. Russell, and P. J. Schaeffer (2012). Acclimatization of seasonal energetics in Northern Cardinals (Cardinalis cardinalis) through plasticity of metabolic rates and ceilings. Journal of Experimental Biology 215: 2418–2424. Close , 100 Laskey, A. R. (1944). A study of the Cardinal in Tennessee. Wilson Bulletin 56: 27–44. Close , 104 Rogers, C. M., and C. J. Rogers (1990). Seasonal variation in daily mass amplitude and minimum body mass: A test of a recent model. Ornis Scandinavica 21: 105–114. Close ). Note, avian mass can vary throughout the day as well as the year, and without information on time of day or season when mass was measured, comparisons are problematic, including for some of the presented data. No clear trend of either sex being more massive; in Tennessee, average male mass 45.1 g (n = 85), average female mass 43.0 g (n = 98; 100 Laskey, A. R. (1944). A study of the Cardinal in Tennessee. Wilson Bulletin 56: 27–44. Close ); however, females were on average more massive than males in southern Indiana, western Ohio, and south-central Wisconsin (Appendix 1). Sgueo et al. (102 Sgueo, C., M. E. Wells, D. E. Russell, and P. J. Schaeffer (2012). Acclimatization of seasonal energetics in Northern Cardinals (Cardinalis cardinalis) through plasticity of metabolic rates and ceilings. Journal of Experimental Biology 215: 2418–2424. Close ) found higher body mass in non-breeding season individuals in a southwestern Ohio population (sexes combined) (47.2 g ± 0.9 SD, n = 22) than in breeding season individuals (41.5 g ± 0.3 SD, n = 102); sex ratios for each sampling period not reported. This mass difference was attributed to significantly higher fat scores observed in nonbreeding individuals, as Sgueo et al. (102 Sgueo, C., M. E. Wells, D. E. Russell, and P. J. Schaeffer (2012). Acclimatization of seasonal energetics in Northern Cardinals (Cardinalis cardinalis) through plasticity of metabolic rates and ceilings. Journal of Experimental Biology 215: 2418–2424. Close ) found no difference in pectoralis muscle mass between breeding and nonbreeding individuals.