Breeding

Testicular Cycle

Unlike other migrant passerines (70 species examined), sperm emissions in Rose-breasted Grosbeaks observed during spring migration, when birds are far south of their breeding range (Quay 1985a Quay, W. B. (1985). Cloacal sperm in spring migrants: occurrence and interpretation. Condor 87: 273–280. Close ). Sperm release also observed in males newly arrived on breeding grounds; these males usually closely attended by a female; first inseminations of females in Missouri were clustered during the period 4–9 May (Quay 1989b Quay, W. B. (1989). Timing of sperm releases and inseminations in resident emberizids: A comparative study. Condor 91: 941–961. Close ).

Pair Formation

Timing of pair formation unknown; some pairing may occur prior to arrival at nesting territory (Dunham 1966c Dunham, D. W. (1966). Territorial and sexual behavior in the Rose-breasted Grosbeak, Pheucticus ludovicianus. Zeitschrift für Tierpsychologie 23: 438–451. Close , Quay 1989b Quay, W. B. (1989). Timing of sperm releases and inseminations in resident emberizids: A comparative study. Condor 91: 941–961. Close ). Males arrive first, separately over several days or at once in groups, females a few days later (Dunham 1966c Dunham, D. W. (1966). Territorial and sexual behavior in the Rose-breasted Grosbeak, Pheucticus ludovicianus. Zeitschrift für Tierpsychologie 23: 438–451. Close , Francis and Cooke 1990 Francis, C. M., and F. Cooke (1990). Differential timing of spring migration in Rose-breasted Grosbeaks. Journal of Field Ornithology 61: 404–412. Close ). Earliest males apparently stay to breed, migrants move through for several weeks after (Dunham 1966c Dunham, D. W. (1966). Territorial and sexual behavior in the Rose-breasted Grosbeak, Pheucticus ludovicianus. Zeitschrift für Tierpsychologie 23: 438–451. Close ). See Migration: timing and routes, above, for arrival dates.

Nest-Building

In Tennessee, commences in second week of May (Nicholson 1997o Nicholson, C. P. (1997). Rose-breasted Grosbeak. In Atlas of the Breeding Birds of Tennessee (C. P. Nicholson, Editor). University of Tennessee Press, Knoxville, TN, USA. pp. 325–327. Close ) and in Ohio, second half of May (Peterjohn and Rice 1991 Peterjohn, B. G., and D. L. Rice (1991). The Ohio Breeding Bird Atlas. Ohio Department of Natural Resources, Columbus, OH, USA. Close ). In northerly parts of the range, nests may not be initiated until late May (Ontario) or Jun (Saskatchewan; Macoun and Macoun 1909 Macoun, J., and J. M. Macoun (1909). Catalogue of Canadian Birds. Government Printing Bureau, Ottawa, Ontario, Canada. Close , VEW). Con-struction takes 2–5 d.

First/Later Broods Per Season

See Figure 4 . Throughout range, laying from mid-May through Jul. Range of first egg dates in New York, 18 May–5 Jun (Watts 1935 Watts, G. E. (1935). Life history of the Rose-breasted Grosbeak (Hedymeles ludoviciana). M.S. thesis, Cornell University, Ithaca, NY, USA. Close ); s. New England, 23 May–15 Jun (Forbush 1929 Forbush, E. H. (1929). Birds of Massachusetts and Other New England States, Part 3: Land Birds from Sparrows to Thrushes. Massachusetts Department of Agriculture, Boston, MA, USA. Close ); Ontario, 10 May–16 Jul (Peck and James 1987 Peck, G. K., and R. D. James (1987). Breeding Birds of Ontario: Nidiology and Distribution. Volume 2: Passerines. Miscellaneous Publications of the Royal Ontario Museum, Toronto, ON, Canada. Close ); Saskatchewan, 21 Jun (Macoun and Macoun 1909 Macoun, J., and J. M. Macoun (1909). Catalogue of Canadian Birds. Government Printing Bureau, Ottawa, Ontario, Canada. Close ). Egg dates in Quebec mid-May to mid-Jul (Pelletier and Dauphin 1996 Pelletier, R., and D. Dauphin (1996). Rose-breasted Grosbeak. In The Breeding Birds of Quebec: Atlas of the Breeding Birds of Southern Québec (J. Gauthier and Y. Aubry, Editors). Association québecoise des groupes d'ornithologues, Province of Quebec Society for the protection of birds, Canadian Wildlife Service, Environent, Québec Region, Montréal, Canada. pp. 954–957. Close ), in Maritime Provinces of Canada, early Jun to mid-Jul (Erskine 1992a Erskine, A. J. (1992). Atlas of Breeding Birds of the Maritime Provinces. Nova Scotia Museum, Halifax, NS, Canada. Close ). Single peak in laying dates; in Ontario, 40% of egg dates were in period 30 May–10 Jun (n = 250; Peck and James 1987 Peck, G. K., and R. D. James (1987). Breeding Birds of Ontario: Nidiology and Distribution. Volume 2: Passerines. Miscellaneous Publications of the Royal Ontario Museum, Toronto, ON, Canada. Close ); 32% of egg dates in 1996–1998 were in period 30 May–1 Jun (n = 62; CWS unpubl.).

Second Brood Per Season

Pairs generally single-brooded (Watts 1935 Watts, G. E. (1935). Life history of the Rose-breasted Grosbeak (Hedymeles ludoviciana). M.S. thesis, Cornell University, Ithaca, NY, USA. Close , Bent 1968b 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 ), although second broods suspected to occur infrequently in Ontario (Langley 1976 Langley, P. J. W. (1976). The breeding behavior and reproductive strategy of the Rose-breasted Grosbeak (Pheucticus ludovicianus). M.S. thesis, University of Western Ontario, London, ON, Canada. Close , Peck and James 1998 Peck, G. K., and R. D. James (1998). Breeding birds of Ontario: nidiology and distribution: passerines (First revision - part C: tanagers to Old World sparrows). Ontario Birds 16: 111–127. Close ); confirmed in semicaptivity (Ivor 1944 Ivor, H. R. (1944). Bird study and semi-captive birds: the Rose-breasted Grosbeak. Wilson Bulletin 56: 91–104. Close ). One instance in Emmet Co., MI, of extreme overlap in first and second nestings, in which second clutch was initiated when young of first brood were 2–6 d old (Rothstein 1973a Rothstein, S. I. (1973). Extreme overlap between first and second nestings in the Rose-breasted Grosbeak. Wilson Bulletin 85: 242–243. Close ).

Selection Process

Little information. Male may help select nest site. Roberts (Roberts 1932c Roberts, T. S. (1932). The Birds of Minnesota. Volume 1. University of Minnesota Press, Minneapolis, MN, USA. Close ) reported observations of both male and female settling into an appropriate fork and turning around several times, as if to test suitability.

Microhabitat

In Ontario, nest sites typically located in forest openings characterized by relatively more open canopy and subcanopy than randomly selected sites (VEW). Nest-site selection not related to number or size of trees, shrub cover, sapling cover, or ground cover within a 5-m radius (VEW). Information needed on microhabitat within range outside Ontario.

Site Characteristics

Nests located in a wide variety of habitats, including deciduous, mixed, and coniferous woodlands, overgrown fields and pastures, shrubby road and rail rights-of-way, in gardens, parks, residential areas.

From Peck and James 1987 Peck, G. K., and R. D. James (1987). Breeding Birds of Ontario: Nidiology and Distribution. Volume 2: Passerines. Miscellaneous Publications of the Royal Ontario Museum, Toronto, ON, Canada. Close and VEW, Ontario. Nests placed in various trees, shrubs, and vines, more often in vertical forks or crotches than on horizontal limbs. Saplings more often selected than tall trees. Deciduous saplings, shrubs, and vines (87% [Peck and James 1987 Peck, G. K., and R. D. James (1987). Breeding Birds of Ontario: Nidiology and Distribution. Volume 2: Passerines. Miscellaneous Publications of the Royal Ontario Museum, Toronto, ON, Canada. Close ], 76% [VEW]) preferred over coniferous species. Plant species most commonly selected include maple (Acer) sp. and red-berried elder (Sambucus pubens). Coniferous species include balsam fir (Abies balsamea), eastern hemlock (Tsuga canadensis), and spruce (Picea spp.). Nests located in both wet areas (swamps, bogs, swales, moist woods) and dry upland areas. One nest reported on rocky outcropping.

Nest heights ranged from 0.8 to 16.8 m (n = 357), averaged 6 m (n = 50; Scott 1998b Scott, D. M. (1998). Laying hours and other nesting data of Rose-breasted Grosbeaks. Ontario Birds 16: 88–93. Close ). Information needed on nest-site characteristics within range outside Ontario.

Construction Process

Quay (Quay 1989b Quay, W. B. (1989). Timing of sperm releases and inseminations in resident emberizids: A comparative study. Condor 91: 941–961. Close ) estimated that selection and establishment of a territory and nest-building take 4–9 d. Watts (Watts 1935 Watts, G. E. (1935). Life history of the Rose-breasted Grosbeak (Hedymeles ludoviciana). M.S. thesis, Cornell University, Ithaca, NY, USA. Close ) concluded that nest-building lasts an average of 5 d and is conducted from dawn until dusk. A semicaptive Rose-breasted Grosbeak completed nest-building in approximately 2 d, and first egg laid the day before nest completion (Ivor 1944 Ivor, H. R. (1944). Bird study and semi-captive birds: the Rose-breasted Grosbeak. Wilson Bulletin 56: 91–104. Close ). Female generally locates appropriate twigs; both male and female construct.

Structure And Composition Matter

Nest is a loose, open cup constructed of coarse sticks, twigs, coarse grasses, weed stems, decayed leaves or straw lined with fine twigs, rootlets, or hair (Baicich and Harrison 1997 Baicich, P. J., and C. Harrison (1997). A Guide to the Nests, Eggs, and Nestlings of North American Birds. 2nd edition. Academic Press, San Diego, California, USA. Close ). No cementing agent used. In Ontario, nest exteriors usually twigs, less often plant stalks, fibers, coarse grasses, pine needles, bark strips, vine tendrils, and flower heads; linings usually fine grasses and rootlets, sometimes fine twigs, plant stalks and fibers, pine needles, leaf and fruit stems, leaves, bark shreds, and feathers (Peck and James 1987 Peck, G. K., and R. D. James (1987). Breeding Birds of Ontario: Nidiology and Distribution. Volume 2: Passerines. Miscellaneous Publications of the Royal Ontario Museum, Toronto, ON, Canada. Close ). Often nests are so thinly constructed that eggs can be seen from below through nest (Peck and James 1987 Peck, G. K., and R. D. James (1987). Breeding Birds of Ontario: Nidiology and Distribution. Volume 2: Passerines. Miscellaneous Publications of the Royal Ontario Museum, Toronto, ON, Canada. Close ). Although nest appears flimsy, incorporation of forked twigs such as Geum canadense may result in added strength without additional bulk (Wyatt 1997 Wyatt, V. E. (1997). Use of Anemone canadensis in Rose-breasted Grosbeak nests. Ontario Birds 15: 74–75. Close ).

Dimensions

In Ontario, 8 nests measured 9–20 cm in diameter, 7–15 cm inside diameter, 4–12 cm outside depth and 3–9 cm inside depth (Peck and James Peck and James 1987 Peck, G. K., and R. D. James (1987). Breeding Birds of Ontario: Nidiology and Distribution. Volume 2: Passerines. Miscellaneous Publications of the Royal Ontario Museum, Toronto, ON, Canada. Close , Peck and James 1998 Peck, G. K., and R. D. James (1998). Breeding birds of Ontario: nidiology and distribution: passerines (First revision - part C: tanagers to Old World sparrows). Ontario Birds 16: 111–127. Close ). From collections of Western Foundation for Vertebrate Zoology (WFVZ), outside diameter and depth of 1 Kansas nest: 13 × 7.5 cm; inside diameter and depth: 8 × 4 cm. Outside diameter and depth of 4 New York and Maryland nests 10–15 × 5–9.5 cm; inside diameter and depth: 6–8 × 4–4.5 cm.

Microclimate

No information.

Maintenance Or Reuse Of Nests, Alternate Nests

New nest is built for each nesting attempt. One report exists of a nest reused in 2 successive years without apparent maintenance or renovation (Friesen et al. 1999b Friesen, L. E., V. E. Wyatt, and M. D. Cadman (1999). Nest reuse by Wood Thrush and Rose-breasted Grosbeak. Wilson Bulletin 111: 133–134. Close ).

Nonbreeding Nests

None recorded.

Shape

Subelliptical to short subelliptical (Baicich and Harrison 1997 Baicich, P. J., and C. Harrison (1997). A Guide to the Nests, Eggs, and Nestlings of North American Birds. 2nd edition. Academic Press, San Diego, California, USA. Close ).

Size

Length and breadth of 50 eggs averaged 24.6 × 17.7 mm; extremes 26.7 × 18.6, 25.7 × 19.1, 20.3 × 17.6, 23.4 × 16.3 mm (Bent 1968b 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 ). From collections of WFVZ, length 24.3 mm (range 22.32–27.17), breadth 17.6 mm (range 16.3–18.8 [n = 85]; R. Corado pers. comm.).

Mass

From collections of WFVZ, mass of empty shell 0.215 g (range 0.161–0.259 [n = 85]; R. Corado pers. comm.). No information on mass of intact eggs.

Color

Pale green, blue, or bluish green, blotched and speckled with reddish brown or purplish red. Markings sparse at narrow end, increasing in density toward larger end (Ehrlich et al. 1988 Ehrlich, P. R., D. S. Dobkin, and D. Wheye (1988). The Birder's Handbook. A Field Guide to the Natural History of North American Birds, Including All Species That Regularly Breed North of Mexico. Simon and Schuster Inc., New York, NY, USA. Close , Baicich and Harrison 1997 Baicich, P. J., and C. Harrison (1997). A Guide to the Nests, Eggs, and Nestlings of North American Birds. 2nd edition. Academic Press, San Diego, California, USA. Close ).

Surface Texture

Smooth, slightly glossy (Baicich and Harrison 1997 Baicich, P. J., and C. Harrison (1997). A Guide to the Nests, Eggs, and Nestlings of North American Birds. 2nd edition. Academic Press, San Diego, California, USA. Close ).

Eggshell Thickness

No information.

Clutch Size

In Ontario, clutches of 226 nests ranged from 1 to 5 eggs, mode 4 (41%; Peck and James 1987 Peck, G. K., and R. D. James (1987). Breeding Birds of Ontario: Nidiology and Distribution. Volume 2: Passerines. Miscellaneous Publications of the Royal Ontario Museum, Toronto, ON, Canada. Close ). Average clutch size of 11 nests in Iowa 3.27 (Best and Stauffer 1980 Best, L. B., and D. F. Stauffer (1980). Factors affecting nesting success in riparian bird communities. Condor 82: 149–157. Close ). Across breeding range, clutches of 151 nests ranged from 3 to 5, mode 4 (67%; WFVZ, R. Corado pers. comm.).

Egg-Laying

Little information on timing of initiation (see Nest, above). Eggs laid on consecutive days, at intervals of approximately 24 h, at least 1 h and as much as 3 h after sunrise (Scott 1998b Scott, D. M. (1998). Laying hours and other nesting data of Rose-breasted Grosbeaks. Ontario Birds 16: 88–93. Close ).

Onset Of Broodiness And Incubation In Relation To Laying

Incubation usually begins when penultimate egg is laid (Scott 1998b Scott, D. M. (1998). Laying hours and other nesting data of Rose-breasted Grosbeaks. Ontario Birds 16: 88–93. Close ).

Incubation Patch

Female has single ventral brood patch. A partial brood patch develops in some males (Pyle 1997c Pyle, P. (1997). Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. Close ).

Incubation Period

Twelve to 13 d (Ivor 1944 Ivor, H. R. (1944). Bird study and semi-captive birds: the Rose-breasted Grosbeak. Wilson Bulletin 56: 91–104. Close ); 12 d (Scott 1998b Scott, D. M. (1998). Laying hours and other nesting data of Rose-breasted Grosbeaks. Ontario Birds 16: 88–93. Close ); 11–14 d (Peck and James 1998 Peck, G. K., and R. D. James (1998). Breeding birds of Ontario: nidiology and distribution: passerines (First revision - part C: tanagers to Old World sparrows). Ontario Birds 16: 111–127. Close ). Eggs in clutch hatch asynchronously, up to 48 h apart (Scott 1998b Scott, D. M. (1998). Laying hours and other nesting data of Rose-breasted Grosbeaks. Ontario Birds 16: 88–93. Close ).

Parental Behavior

During the day, male does approximately one-third of incubation, female the remainder (Watts 1935 Watts, G. E. (1935). Life history of the Rose-breasted Grosbeak (Hedymeles ludoviciana). M.S. thesis, Cornell University, Ithaca, NY, USA. Close ). At night, female typically incubates. Eggs rarely left unattended. Both sexes approach incubating partner and sing softly to exchange places (Ivor 1944 Ivor, H. R. (1944). Bird study and semi-captive birds: the Rose-breasted Grosbeak. Wilson Bulletin 56: 91–104. Close , VEW). Male frequently sings while on or near nest. Incubating males responded to taped playbacks but would not leave nest until replaced by mate (Kroodsma 1974c Kroodsma, R. L. (1974). Species-recognition behavior of territorial male Rose-breasted and Black-headed grosbeaks (Pheucticus). Auk 91: 54–64. Close ).

Hardiness Of Eggs Against Temperature Stress/Effect Of Egg Neglect

No information.

No information.

Condition At Hatching

Altricial, eyes closed, sparse white down on capital, dorsal, crural, femoral, and alular tracts. Average body mass 4.5 g, length 5 cm (Watts 1935 Watts, G. E. (1935). Life history of the Rose-breasted Grosbeak (Hedymeles ludoviciana). M.S. thesis, Cornell University, Ithaca, NY, USA. Close ).

Growth And Development

In New York State, on days 2–6 after hatching, young gained at least 3 g/d; average mass on day 7 was 24.9 g, day 8, 26 g, day 9 (usually day before fledging), 27.5 g, length 10 cm (Watts 1935 Watts, G. E. (1935). Life history of the Rose-breasted Grosbeak (Hedymeles ludoviciana). M.S. thesis, Cornell University, Ithaca, NY, USA. Close ). Quills appear on day 5; nearly fully feathered by day 12 (Bent 1968b 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 ). Sexes can be distinguished at age of 5 d; young male has pink wing-linings. Call note made by young 6 d after hatching; young follow visual stimuli with eyes at 7 d (Dunham Dunham 1966a Dunham, D. W. (1966). Maintenance activities of the Rose-breasted Grosbeak. Wilson Bulletin 78: 68–78. Close , Dunham 1966c Dunham, D. W. (1966). Territorial and sexual behavior in the Rose-breasted Grosbeak, Pheucticus ludovicianus. Zeitschrift für Tierpsychologie 23: 438–451. Close ). Freeze response to threatening stimuli first observed 7, 8, or 9 d after hatching (Ivor 1944 Ivor, H. R. (1944). Bird study and semi-captive birds: the Rose-breasted Grosbeak. Wilson Bulletin 56: 91–104. Close , Dunham 1965 Dunham, D. W. (1965). Agonistic behavior in captive Rose-breasted Grosbeaks (Pheucticus ludovicianus). Behaviour 27: 160–173. Close ). Egg tooth disappears 13 d after hatching (Ivor 1944 Ivor, H. R. (1944). Bird study and semi-captive birds: the Rose-breasted Grosbeak. Wilson Bulletin 56: 91–104. Close ).

Brooding

During the day, brooding shared about equally between male and female (Watts 1935 Watts, G. E. (1935). Life history of the Rose-breasted Grosbeak (Hedymeles ludoviciana). M.S. thesis, Cornell University, Ithaca, NY, USA. Close ). Brooding for periods ranging from 1 h 19 min to 6 h 54 min (Bent 1968b 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 ). No data on brooding changes throughout nestling period.

Feeding

Number of feeding visits at least 7/h (Watts 1935 Watts, G. E. (1935). Life history of the Rose-breasted Grosbeak (Hedymeles ludoviciana). M.S. thesis, Cornell University, Ithaca, NY, USA. Close ) to 10/h (Ivor 1944 Ivor, H. R. (1944). Bird study and semi-captive birds: the Rose-breasted Grosbeak. Wilson Bulletin 56: 91–104. Close ). Twenty-eight feeding visits by male in 30 min (Bent 1968b 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 ). In one full day of observation, 22–58 feeding visits/h by parents to nestlings of unknown age (E. H. Forbush in McAtee 1908a McAtee, W. L. (1908). Food habits of the grosbeaks. U.S. Department of Agriculture, Biological Survey, Bulletin 32. Close ); frequency of feeding visits highest between 06:00 and 08:00 and after 16:00. In nearly 60 h of observation, 74% of feedings by female (Bent 1968b 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 ). Little information as to sex differences in feeding behavior. No information on changes in feeding rate with number or age of young.

Diet of nestlings approximately three-quarters animal matter (McAtee 1908a McAtee, W. L. (1908). Food habits of the grosbeaks. U.S. Department of Agriculture, Biological Survey, Bulletin 32. Close ). Most common food item was insect larvae; seeds and other insects made up much smaller proportion of diet (Bent 1968b 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 ). Insects often crushed before being fed to nestlings (Dunham 1966a Dunham, D. W. (1966). Maintenance activities of the Rose-breasted Grosbeak. Wilson Bulletin 78: 68–78. Close ). See Food habits: diet, above, for food types.

Nest Sanitation

Parents eat feces of newly hatched young (Ivor 1944 Ivor, H. R. (1944). Bird study and semi-captive birds: the Rose-breasted Grosbeak. Wilson Bulletin 56: 91–104. Close ). Later, either parent carries away fecal sacs (Watts 1935 Watts, G. E. (1935). Life history of the Rose-breasted Grosbeak (Hedymeles ludoviciana). M.S. thesis, Cornell University, Ithaca, NY, USA. Close ).

Carrying Of Young

Not known to occur.

One instance of semicaptive male feeding another semicaptive pair's brood on several occasions when brood was neglected (Ivor 1944 Ivor, H. R. (1944). Bird study and semi-captive birds: the Rose-breasted Grosbeak. Wilson Bulletin 56: 91–104. Close ). No reported cooperative breeding for wild birds.

Frequency Of Occurrence, Seasonal Or Geographic Variation

Reported by Bent (Bent 1968b 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 ) and Ehrlich et al. (Ehrlich et al. 1988 Ehrlich, P. R., D. S. Dobkin, and D. Wheye (1988). The Birder's Handbook. A Field Guide to the Natural History of North American Birds, Including All Species That Regularly Breed North of Mexico. Simon and Schuster Inc., New York, NY, USA. Close ) to be a common Brown-headed Cowbird (Molothrus ater) host, but quantitative data do not support these generic statements (see Table 2). No other nest parasites known. Studies in e. North America show relatively low rates of parasitism compared to other open-cup-nesting species. In Ontario, parasitism rates ranged from 3.6 to 10%. In Quebec, 7.1% of 42 nests parasitized (Terrill 1961 Terrill, L. M. (1961). Cowbird hosts in southern Quebec. Canadian Field-Naturalist 75: 2–11. Close ). Rates of 5% in New York (n = 20; Link and Hahn 1996 Link, W. A., and D. C. Hahn (1996). Empirical Bayes estimation of proportions with application to cowbird parasitism rates. Ecology 77: 2528–2537. Close ), 0% in Illinois (n = 3; Robinson 1992 Robinson, S. K. (1992). Population dynamics of breeding Neotropical migrants in a fragmented Illinois landscape. In Ecology and Conservation of Neotropical Migrant Landbirds (J. M. Hagen III and D. W. Johnston, Editors). Smithsonian Instute Press, Washington, DC, USA. pp. 408–418. Close ) and Iowa (n = 18; Best and Stauffer 1980 Best, L. B., and D. F. Stauffer (1980). Factors affecting nesting success in riparian bird communities. Condor 82: 149–157. Close ). Cowbird eggs or young in 23% of 70 nests of Rose-breasted, Black-headed, and hybrid grosbeak pairs in the Great Plains area of maximum hybridization (Anderson and Daugherty 1974 Anderson, B. W., and R. J. Daugherty (1974). Characteristics and reproductive biology of grosbeaks (Pheucticus) in the hybrid zone in South Dakota. Wilson Bulletin 86: 1–11. Close ).

Timing Of Laying In Relation To Host'S Laying

No information.

Response To Parasitic Mother, Eggs, Or Nestlings

No information. Aggressive behavior and nest-tending by both parents may result in less vulnerability to brood parasitism compared to other species (Friesen et al. 1999c Friesen, L., M. D. Cadman, and R. J. MacKay (1999). Nesting success of neotropical migrant songbirds in a highly fragmented landscape. Conservation Biology 13(2): 338–346. Close ).

Effects Of Parasitism On Host

Limited Ontario samples of successful, parasitized nests indicate number of Rose-breasted Grosbeak young fledged/successful nest unaffected by parasitism (Friesen et al. 1999c Friesen, L., M. D. Cadman, and R. J. MacKay (1999). Nesting success of neotropical migrant songbirds in a highly fragmented landscape. Conservation Biology 13(2): 338–346. Close [n = 4], CWS unpubl. [n = 3]). Parasitism did not reduce ability of Rose-breasted Grosbeaks to fledge at least 1 host young (Burke and Nol 2000 Burke, D. M., and E. Nol (2000). Landscape and fragment size effects on reproductive success of forest-breeding birds in Ontario. Ecological Applications 10(6): 1749–1761. Close ). In Illinois, no nests failed due to brood parasitism (n = 9; Best and Stauffer 1980 Best, L. B., and D. F. Stauffer (1980). Factors affecting nesting success in riparian bird communities. Condor 82: 149–157. Close ).

Success Of Parasite With This Host

No Brown-headed Cowbirds fledged from a limited sample (n = 6) of parasitized nests in Ontario (CWS unpubl.).

Departure From Nest, Growth

Nestlings leave nest as early as 9 d of age and as late as 12 d, generally at about 10 d (Scott 1998b Scott, D. M. (1998). Laying hours and other nesting data of Rose-breasted Grosbeaks. Ontario Birds 16: 88–93. Close , VEW).

Association With Parents Or Other Young

Young dependent on adults for about 3 wk after fledging. Maintain family groups throughout summer until migration (Watts 1935 Watts, G. E. (1935). Life history of the Rose-breasted Grosbeak (Hedymeles ludoviciana). M.S. thesis, Cornell University, Ithaca, NY, USA. Close ). Where infrequent second nesting is initiated, male feeds nestlings or fledged young while female renests (H. R. Ivor in Bent 1968b 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 , Rothstein 1973a Rothstein, S. I. (1973). Extreme overlap between first and second nestings in the Rose-breasted Grosbeak. Wilson Bulletin 85: 242–243. Close ).

Ability To Get Around, Feed, And Care For Self

No information.

No information.