Movements and Migration

A long-distance Nearctic‒Neotropical migrant that breeds in North America and overwinters in South America. Its secretive behavior and preference for dense undergrowth have made it difficult to define migratory routes, migration timing, and stopover ecology and behavior. Information needed on dispersal and site fidelity.

Natal Philopatry and Dispersal

Information needed.

Adult Fidelity to Breeding Site and Dispersal

Leston et al. (126 Leston, L., E. Bayne, and F. Schmiegelow (2018). Long-term changes in boreal forest occupancy within regenerating harvest units. Forest and Ecology Management 421:40–53. Close ) conducted a 23-year study of occupancy rates of several boreal species in northern Alberta. They recorded whether a species returned each year to the same point-count station to assess the impact of forest harvesting, forest regeneration, and El Niño events. Connecticut Warbler was among seven species affected by El Niño. Following strong El Niño years, Connecticut Warbler, Bay-breasted Warbler (Setophaga castanea), Common Yellowthroat (Geothlypis trichas), Tennessee Warbler (Leiothlypis peregrina), LeConte's Sparrow (Ammospiza leconteii), Lincoln's Sparrow (Melospiza lincolnii), and Alder Flycatcher (Empidonax alnorum) were more likely to return to the same breeding station they had visited in prior years. Extinction probabilities, defined as the failure to return to a point-count location that had been visited in previous years, were less likely for these species in years with a high El Niño index. More information needed.

Fidelity to Overwintering Home Range

Information needed.

This species migrates later in both spring and fall than most other New World warblers. Generally rarely detected by birders in migration owing to its elusive behavior and tendency to occur in dese understory habitats, but bird-banding efforts usually reveal larger numbers of migrants (e.g., at Cape May, New Jersey; 127 Sibley, D. A. (1997). Birds of Cape May. Second edition. Cape May Bird Observatory, New Jersey Audubon Society, Cape May, NJ, USA. Close ).

Chapman (109 Chapman, F. M. (1907). The Warblers of North America. D. Appleton & Company, New York, NY, USA. Close ) believed that in spring the Connecticut Warbler migrates northwest through the Mississippi Valley, and in fall it moves east across Canada, then south along the Atlantic Coast. Research by McKinnon et al (128 McKinnon, E. A., C. Artuso, and O. P. Love (2017). The mystery of the missing warbler. Ecology 98:1970–1972. Close ) and Hallworth et al. (64 Hallworth M. T., E. Bayne, E. McKinnon, O. Love, J. A. Tremblay, B. Drolet, J. Ibarzabal, S. Van Wilgenburg, and P. P. Marra (2021). Habitat loss on the breeding grounds is a major contributor to population declines in a long-distance migratory songbird. Proceedings of the Royal Society B 288(1949). Close ) using geolocators and eBird data supported Chapman's idea with some modifications. Fall migrants initially leave the breeding grounds and migrate to the Atlantic Coast, followed by transoceanic flights, first to the Greater Antilles and then to overwintering grounds in South America (see Migration Routes, below).

Post-Breeding

After departing the breeding grounds, migrates southeast towards the Atlantic Coast. Fall migration was originally thought to involve movement along the Atlantic coast with birds later moving on to the Greater Antilles and eventually to South America (109 Chapman, F. M. (1907). The Warblers of North America. D. Appleton & Company, New York, NY, USA. Close ). However, McKinnon et al. (128 McKinnon, E. A., C. Artuso, and O. P. Love (2017). The mystery of the missing warbler. Ecology 98:1970–1972. Close ) finally provided concrete evidence of transoceanic flights during fall migration using geolocators. They found that the Connecticut Warbler makes an approximately two-day long, overwater flight from eastern North America to the Greater Antilles, followed by a second flight of 600–800 km across the Caribbean Sea to overwintering grounds in South America. Arrival on Caribbean islands occurred from early to mid-October (128 McKinnon, E. A., C. Artuso, and O. P. Love (2017). The mystery of the missing warbler. Ecology 98:1970–1972. Close ). This timing roughly corresponds with that of records on Bermuda (mainly late September to mid-October; eBird), and the 75 individuals that were grounded there during Hurricane Emily on 26 September 1987 (120 Amos, E. J. R. (1991). A Guide to the Birds of Bermuda. Corncrake, Warwick, Bermuda. Close ). Arrivals in South America occurred towards the end of October. Hallworth et al. (64 Hallworth M. T., E. Bayne, E. McKinnon, O. Love, J. A. Tremblay, B. Drolet, J. Ibarzabal, S. Van Wilgenburg, and P. P. Marra (2021). Habitat loss on the breeding grounds is a major contributor to population declines in a long-distance migratory songbird. Proceedings of the Royal Society B 288(1949). Close ) also used geolocators to follow Connecticut Warblers (n = 9) from four natural populations across Canada and in Minnesota. Based on their data, the average arrival on the Atlantic coast was 10 September (± 6.63 days). The average departure date for the long-distance flight over the Atlantic Ocean was 10 October (± 5.82 days), with an average transoceanic flight lasting 3 ± 0.65 days. The average arrival date on the overwintering area was 9 November ± 3.52 days. Both McKinnon et al. (128 McKinnon, E. A., C. Artuso, and O. P. Love (2017). The mystery of the missing warbler. Ecology 98:1970–1972. Close ) and Hallworth et al. (64 Hallworth M. T., E. Bayne, E. McKinnon, O. Love, J. A. Tremblay, B. Drolet, J. Ibarzabal, S. Van Wilgenburg, and P. P. Marra (2021). Habitat loss on the breeding grounds is a major contributor to population declines in a long-distance migratory songbird. Proceedings of the Royal Society B 288(1949). Close ) speculated that some birds do not stop in the eastern Caribbean and fly directly to South America.

Peak southbound migration in the western part of the breeding range begins late August; latest departure dates range from early to late September in Alberta (85 Salt, W. R. (1973). Alberta vireos and wood warblers: families Vireonidae and Parulidae, distribution and breeding. Edmonton Provincial Museum and Archives of Alberta, Edmonton, AB, Canada. Close ). In British Columbia, adults may leave breeding areas as early as mid-July followed by first-fall birds in August (93 Cooper, J. M., K. A. Enns and M. G. Shepard (1997). Status of the Connecticut Warbler in British Columbia. British Columbia Ministry of the Environment, Lands and Parks, Wildlife Branch, Wildlife Working Report No. WR-83. Victoria, BC, Canada. Close ). It departs breeding grounds in Minnesota and Michigan late August–early October (67 Janssen, R. B. (1987). Birds in Minnesota. University of Minnesota Press, Minneapolis, Minnesota, USA. Close , 129 Granlund, J., G. A. McPeek, and R. J. Adams (1994). The Birds of Michigan. Indiana University Press, Bloomington, IN, USA. Close ); migrants have been captured from 20 August to 20 September in southeastern Minnesota (130 Weisbrod, A. R., C. J. Burnett, J. G. Turner, and D. W. Warner (1993). Migrating birds at a stopover site in the Saint Croix River valley. Wilson Bulletin 105:265–284. Close ). At Eau Clair in west-central Wisconsin, individuals were killed by tower collisions between 23 August and 12 October (up to 300 in one fall season and 140 in a single night), though some individuals are recorded as early as mid-August and as late as late October (102 Robbins, S. D., Jr. (1991). Wisconsin Birdlife: Population and Distribution, Past and Present. University of Wisconsin Press, Madison, Wisconsin, USA. Close ). In Ohio, it arrives by the last week of August and peaks 10 September–5 October; the latest records in mid-October (131 Peterjohn, B. G. (2001). The Birds of Ohio with Breeding Bird Atlas Maps. Wooster Book Company, Wooster, OH, USA. Close ). Rare from early September to late October in Kentucky (132 Monroe, B. L., Jr. (1994). The Birds of Kentucky. Indiana University Press, Bloomington, IN, USA. Close ). In Massachusetts, late August–early October, with most records along the coast, but some from Berkshires, Connecticut River valley, and west of Boston (112 Veit, R. R., and W. R. Petersen (1993). The Birds of Massachusetts. Massachussetts Audubon Society, Lincoln, Massachusetts, USA. Close ); average arrival of 19 September on Cape Cod (133 Lloyd-Evans, T. L., and J. L. Atwood (2004). 32 years of changes in passerine numbers during spring and fall migrations in coastal Massachusetts. Wilson Bulletin 116(1):1–16. Close ). It occurs more rarely in northern New England and the Maritime Provinces during fall. There are several records from late September to mid-October on Brier Island off the west coast of Nova Scotia (134 Mills, E. L., and L. Laviolette (2011). Birds of Brier Island. Proceedings of the Nova Scotian Institute of Science 46. Close ). It occurs along the coast of New York largely from mid-September to mid-October (113 Bull, J. (1974). Birds of New York State. Doubleday Natural History Press, Garden City, NY, USA. Close ). In coastal New Jersey, peak numbers pass from mid-September to mid-October (135 Leck, C. F. (1984). The Status and Distribution of New Jersey's Birds. Rutgers University Press, New Brunswick, NJ, USA. Close , 127 Sibley, D. A. (1997). Birds of Cape May. Second edition. Cape May Bird Observatory, New Jersey Audubon Society, Cape May, NJ, USA. Close ). Occurs mainly from second week of September to first week of October in Pennsylvania (136 McWilliams, G. M., and D. W. Brauning (2000). The Birds of Pennsylvania. Cornell University Press, Ithaca, NY, USA. Close ). Birds were banded in eastern Maryland from 25 August–21 October (137 Mehlman, D. W. (1990). Migration timing of four uncommon species in Montgomery County. Maryland Birdlife 46(3):79–82. Close ). Eight first-year and four adult migrants were captured from 14 September–23 October at the eastern shore of the Virginia National Wildlife Refuge, with the estimated mean migration date of 29 September (138 Smith, F. M. (2011). Summary of fall Passerine banding on the Eastern Shore of Virginia National Wildlife Refuge: 2009–2010 Seasons. CCB Technical Report 346, Center for Conservation Biology, Williamsburg, VA, USA. Close ). Farther south, fall records become more scarce in Georgia and Florida, mainly along the Atlantic coast (139 Stevenson, H. M., and B. H. Anderson (1994). The Birdlife of Florida. University Press of Florida, Gainesville, Florida, USA. Close , eBird). Fall migrants are rarely recorded in the Mississippi Valley (south of Minnesota) and Gulf coastal states (eBird). For example, it is a rare fall migrant in September in eastern Nebraska (140 Johnsgard, P. A. (2015). Birding Nebraska’s Central Platte Valley and Rainwater Basin. Zea E-Books. Book 36, University of Nebraska, Lincoln, NE, USA. Close ), and very rare in Missouri from mid-August through early October (141 Robbins, M. B. (2018). The Status and Distribution of Birds in Missouri. University of Kansas Libraries, Lawrence, KS, USA. Close ). It is a rare fall migrant along Gulf coasts of Alabama (142 Imhof, T. A. (1976). Alabama Birds. Second Edition. University of Alabama Press, Tuscaloosa, AL, USA. Close ) and casual in eastern Texas (143 Lockwood, M. W., and B. Freeman (2014). The Texas Ornithological Society Handbook of Texas Birds. Louise Lindsey Merrick Natural Environment Series, volume 47. Texas A&M University Press, College Station, TX, USA. Close ). The latest fall record in North America was a first-fall individual recorded on 11 November 2019 in Scarborough, Maine (144 Perlut, N. (2019). Latest documented fall record of Oporornis agilis (Connecticut Warbler) in North America. Northeastern Naturalist 26:12–13. Close ).

Rare, but regularly recorded in the Caribbean in fall migration, September to early November (145 Kirwan, G. M., A. Levesque, M. Oberle, and C. J. Sharpe (2019). Birds of the West Indies. Lynx Edicions, Barcelona, Spain. Close ), with records in the Bahamas, Cayman Islands, Cuba, Hispaniola, Puerto Rico, St. Barthélemy, Guadeloupe, and Barbados (145 Kirwan, G. M., A. Levesque, M. Oberle, and C. J. Sharpe (2019). Birds of the West Indies. Lynx Edicions, Barcelona, Spain. Close ; see eBird). A first-fall female was banded at Harrison's Point on Barbados in November, where it is considered a transient species (146 McNair, D. B., E. B. Massiah, and M. D. Frost (1999). New and rare species of Nearctic landbird migrants during autumn for Barbados and the Lesser Antilles. Caribbean Journal of Science 35(1–2):46–53. Close ). It is considered an occasional fall migrant during October on Guadeloupe (147 Levesque A., and F. Delcroix (2013). Liste des oiseaux de la Guadeloupe (7ème édition). Grande-Terre, Basse-Terre, Marie-Galante, les Saintes, la Désirade, Îlets de la Petite-Terre. Rapport AMAZONA 32. Close ) and nearby La Desirade (148 Levesque A. and F. Delcroix (2016). Liste des oiseaux de l’île de La Désirade (1ère édition). Rapport AMAZONA 44. Close ). Although records suggest that Connecticut Warbler is a rare fall migrant in the Caribbean, geolocator data (128 McKinnon, E. A., C. Artuso, and O. P. Love (2017). The mystery of the missing warbler. Ecology 98:1970–1972. Close , 64 Hallworth M. T., E. Bayne, E. McKinnon, O. Love, J. A. Tremblay, B. Drolet, J. Ibarzabal, S. Van Wilgenburg, and P. P. Marra (2021). Habitat loss on the breeding grounds is a major contributor to population declines in a long-distance migratory songbird. Proceedings of the Royal Society B 288(1949). Close ) indicate that stopover may occur more regularly there. Indeed, it seems likely that the species is under-detected owing to its elusive behavior and association with dense understory.

It arrives in Aruba, Curaçao, Bonaire, and Venezuela from late September and October (57 Hilty, S. L. (2003). Birds of Venezuela. Princeton University Press, Princeton, NJ, USA. Close , 149 Prins, T. G., J. H. Reuter, A. O. Debrot, J. Wattel, and V. Nijman (2009). Checklist of the birds of Aruba, Curacao and Bonaire, South Caribbean. Ardea 97(2):137–268. Close ). Several early to mid-October records are from Aruba; observed in Curaçao from 9 October–13 November; and on Bonaire from 2–15 October (149 Prins, T. G., J. H. Reuter, A. O. Debrot, J. Wattel, and V. Nijman (2009). Checklist of the birds of Aruba, Curacao and Bonaire, South Caribbean. Ardea 97(2):137–268. Close ). It passes through the northwestern coast of Venezuela until early October (121 Bosque, C., and M. Lentino (1987). The passage of North American migratory land birds through xerophytic habitats on the western coast of Venezuela. Biotropica 19:267–273. Close ); four individuals were mist-netted at Tambopata Reserve in southeastern Peru, but only from 3–17 November, suggesting transient individuals (29 Parker, T. A., III (1982). Observations of some unusual rainforest and marsh birds in southeastern Peru. Wilson Bulletin 94(4):477–493. Close , 60 Sorrie, B. A. (2016). Early records of Connecticut Warbler Oporornis agilis in Amazonian Peru. Cotinga 38:46. Close ). An adult female, considered a possible migrant, was mist-netted near Loreto, Peru on 18 November 2012 (125 Martin, J. U. (2017). Connecticut Warbler (Oporornis agilis) in a Peruvian white sand forest habitat. Boletín de la Unión de Ornitólogos del Perú 12:6–8. Close ). The first record west of the Andes and for Ecuador was a first-fall bird captured on 21 November 1996 (150 Jahn, O., M. E. J. Viteri, and K. L. Schuchmann (1999). Connecticut Warbler: a North American migrant new to Ecuador. Wilson Bulletin 111(2):281–282. Close ). Paynter (56 Paynter, R. A., Jr. (1995). Nearctic Passerine Migrants in South America. Publications of the Nuttall Ornithological Club 25, Cambridge, MA, USA. Close ) mentioned a migration record for French Guiana. An adult female mist-netted on 2 November 2014 on an island in Balbina Reservoir in central Amazonian Brazil was believed to be a migrant because of its heavy fat and date of capture (151 Diniz, C, J. D. Wolfe, M. Anciaes, and P. Stouffer (2014). New record of Connecticut Warbler Oporornis agilis in central Amazonian Brazil. Cotinga 36:127. Close ).

Recorded widely (but rarely) west of the main migration (see eBird). For example, there are 6 fall records in Montana, all late August (152 Marks, J. S., P. Hendricks, and D. Casey (2016). Birds of Montana. Buteo Books, Arrington, Virginia, USA. Close ). It is a vagrant along the Pacific Coast. A fall migrant was reported in late October on the west coast of Vancouver Island, British Columbia (153 Dorst, A. (2018). The Birds of Vancouver Island’s West Coast. UBC Press, University of British Columbia, Vancouver, BC, Canada. Close ). It is a regular vagrant along the California coast from September through October (154 Stake, M. M. (2012). Trends in vagrant capture rates at a coastal California banding station (1993–2010). Bird Populations 11:14–21. Close ); e.g., in the late 1900s, there were over 70 fall records in California, including the Farallon Islands, Humboldt Bay, Monterey Bay, Channel Islands, Point Reyes, and one from Death Valley (155 Roberson, D. (1980). Rare Birds of the West Coast of North America. Woodcock Publications, Pacific Grove, CA, USA. Close , 156 Garrett, K., and J. Dunn (1981). Birds of Southern California: Status and Distribution. Los Angeles Audubon Society, Los Angeles, CA, USA. Close , 157 Taylor, D. M., D. F. DeSante, G. R. Geupel, and K. Houghton (1994). Autumn populations of landbirds along central coastal California 1976–1986. Journal of Field Ornithology 65(2):169–185. Close ). Compared to species of similar-sized North American breeding populations, western vagrants of the Connecticut Warbler may be observed less often than expected according to models from Ralph and Wolfe (158 Ralph, C. J. and J. D. Wolfe (2018). Factors affecting the distribution and abundance of autumn vagrant New World warblers in northwestern California and southern Oregon. PeerJ 6:e5881. Close ). They believed that problems detecting birds in dense vegetation and confusion with similar plumages of Mourning Warbler (Geothlypis philadelphia) and MacGillivray's Warbler (Geothlypis tolmiei) may account for the under-representation.

There are very few to no substantiated records (specimens, photographs) in Mexico and northern Central America (e.g., 159 Howell, S. N. G., and S. Webb (1995). A Guide to the Birds of Mexico and Northern Central America. Oxford University Press, New York, NY, USA. Close ). Reported as a fall vagrant on Baja California, Mexico (160 Erickson, R. A., R. Carmona, G. Ruizcampos, M. Iliff, and M. J. Billings (2013). Annotated Checklist of the Birds of Baja California and Baja California Sur, 2nd Edition. North American Birds 66:582–613 Close ), and one report on 1 November from Clipperton Island off western Mexico (161 Howell, S. N. G., P. Pyle, L. B. Spear, and R. L. Pittman (1993). North American migrant birds on Clipperton Atoll. Western Birds 24:73–80. Close ). There is well-documented sight record for 6 October in north-central Nicaragua (162 Chavarría-Duriaux, L., D. C. Hille, and R. Dean (2018). Birds of Nicaragua: A Field Guide. Cornell University Press, Ithaca, NY, USA. Close ; eBird). It is a rare fall transient in Panama, late September–late October; 3 specimen records from Bocas del Toro (163 Wetmore, A., R. F. Pasquier, and S. L. Olson (1984). The Birds of the Republic of Panama, Part 4-Passeriformes: Hirundinidae (Swallows) to Fringillidae (Finches). Smithsonian Miscellaneous Collections 150, Part 4. Close , 164 Ridgely, R. S., and J. A. Gwynne (1989). A Guide to the Birds of Panama with Costa Rica, Nicaragua, and Honduras. Second edition. Princeton University Press, Princeton, NJ, USA. Close ). There are several reports from Costa Rica (124 Stiles, F. G., and A. F. Skutch (1989). A Guide to the Birds of Costa Rica. Cornell University Press, Ithaca, NY, USA. Close , eBird), but these were viewed to lack convincing documentation and were considered hypothetical (165 Dyer, D. and S. N. G. Howell (2023). Birds of Costa Rica. Princeton University Press, NJ, USA. Close ).

Pre-Breeding

The timing of northbound departure from overwintering grounds is not clear, but spring transients (specimens) have been recorded in Venezuela from late April to 9 May (57 Hilty, S. L. (2003). Birds of Venezuela. Princeton University Press, Princeton, NJ, USA. Close ). It is generally reported to migrate through the Caribbean to Florida in spring, though it is only very rarely recorded in the islands (April and May; 166 Raffaele, H. A. (1989). A guide to the birds of Puerto Rico and the Virgin Islands. Princeton University Press, Princeton, NJ, USA. Close , 145 Kirwan, G. M., A. Levesque, M. Oberle, and C. J. Sharpe (2019). Birds of the West Indies. Lynx Edicions, Barcelona, Spain. Close ); it is possible that spring migrants typically fly over the Caribbean, though those that stopover would be very difficult to detect. Spring records include: an adult male banded at Santiago de Cuba, southern Cuba on 22 May (23 León, C. P., M. P. Sánchez, Y. S. Vega, N. V. Dávila, and F. R. Santana (2019). Reporte de la Bijirita de Connecticut (Oporornis agilis; Aves: Parulidae) en el oriente de Cuba. Novitates Caribbaea 14:163–166. Close ); one mist-netted in southwestern Puerto Rico (date unknown, 167 Kornegay, M. E. (2011). Abundance and breeding productivity of resident avian species in Guánica State Forest. M. S. Thesis. North Carolina State University, Raleigh, North Carolina, USA. Close ); one sighting in Dominican Republic (168 Keith, A. R., J. W. Wiley, S. C. Latta, and J. A. Ottenwalder (2003). The Birds of Hispaniola. Haiti and the Dominican Republic: An Annotated Checklist. BOU Check-list 21. British Ornithologists’ Union, Tring, UK. Close ); one report in Jamaica (eBird); several reports from the Bahamas (eBird); no spring records for Aruba, Bonaire, and Curaçao (169 Wells, J. V., and A. C. Wells (2017). Birds of Aruba, Bonaire, and Curaçao. Cornell University Press, Ithaca, NY, USA. Close ). There is one spring report from Bermuda (120 Amos, E. J. R. (1991). A Guide to the Birds of Bermuda. Corncrake, Warwick, Bermuda. Close ).

Spring records are scattered through much of Florida, including the Florida Keys, Atlantic and Gulf coasts, but the species is rare in the panhandle (170 Sprunt, A., Jr. (1954). Florida Birdlife. Coward-McCann, New York, NY, USA. Close , 139 Stevenson, H. M., and B. H. Anderson (1994). The Birdlife of Florida. University Press of Florida, Gainesville, Florida, USA. Close , eBird); most records are from the Atlantic Coast (e.g., a single tower kill of 25 individuals on 7 May near Cape Canaveral; 171 Cruickshank, A. D. (1980). The birds of Brevard County, Florida. Florida Press, Inc., Orlando, FL, USA. Close ). North of Florida, spring records suggest that migrants move northwest and north into the Mississippi and Ohio valleys north to the Great Lakes and central Canada. Migrants have been reported from early May to mid-May at various locations in northern Georgia (e.g., Clarke, Cobb, Clayton, and Murray counties) (172 Hall, R. (2011). From the field. Oriole 76:37–46. Close ). It is a rare transient in Missouri, mainly from mid-May to late May, but occasionally in late April or the first week of June (141 Robbins, M. B. (2018). The Status and Distribution of Birds in Missouri. University of Kansas Libraries, Lawrence, KS, USA. Close ); it primarily is detected in northeastern Missouri, from the St. Louis area 11–24 May (173 Uffman, J. P., and R. N. Douglas (2014). Spring 2014 seasonal report. Bluebird 81:146–164. Close ). It is a rare spring transient in Kentucky; most migrants pass in mid-May, rarely before 1 May (108 Mengel, R. M. (1965). The birds of Kentucky. Ornithological Monographs 3. American Ornithologists' Union, Washington, DC, USA. Close , 132 Monroe, B. L., Jr. (1994). The Birds of Kentucky. Indiana University Press, Bloomington, IN, USA. Close ). In Ohio, it is rare to uncommon with most records from along Lake Erie; generally it arrives around 15 May, but most are recorded 18–30 May; most depart by 1–5 June; stragglers remain until the second week of June (131 Peterjohn, B. G. (2001). The Birds of Ohio with Breeding Bird Atlas Maps. Wooster Book Company, Wooster, OH, USA. Close ). In Illinois, the average arrival date for Chicago is 21 May (n = 15 yr of observation), and for Urbana, 17 May (n = 16 yr of observation) (174 Bohlen, H. D. (1989). The Birds of Illinois. Indiana University Press, Bloomington, IN, USA. Close ). Migrants were detected in southeastern Minnesota (Washington County) from 18–28 May (175 Winker, K., D. W. Warner, and A. R. Weisbrod (1992). Migration of woodland birds at a fragmented inland stopover site. Wilson Bulletin 104(4):580–598. Close , 130 Weisbrod, A. R., C. J. Burnett, J. G. Turner, and D. W. Warner (1993). Migrating birds at a stopover site in the Saint Croix River valley. Wilson Bulletin 105:265–284. Close ).

Most individuals arrive on breeding grounds mid to late May; in Minnesota, most arrive in late May (67 Janssen, R. B. (1987). Birds in Minnesota. University of Minnesota Press, Minneapolis, Minnesota, USA. Close ); in northern Michigan, mid-May to early June (129 Granlund, J., G. A. McPeek, and R. J. Adams (1994). The Birds of Michigan. Indiana University Press, Bloomington, IN, USA. Close ); in Wisconsin, after 20 May, but one early migrant was collected in Milwaukee on 25 April (102 Robbins, S. D., Jr. (1991). Wisconsin Birdlife: Population and Distribution, Past and Present. University of Wisconsin Press, Madison, Wisconsin, USA. Close ). Males arrived on the breeding grounds in south-central Quebec from 27–29 May followed by females from 3–7 June (27 Saulnier, M-C. (2011). Biologie de la reproduction de la Paruline à gorge grise (Oporornis agilis) dans les pinèdes grises du Lac-Saint-Jean, Canada. M.S. thesis, Université du Québec à Chicoutimi, Chicoutimi, QC, Canada. Close ). Peak arrivals occurred by the second week of May in Ontario (176 James, R. D., P. L. McLaren, and J. C. Barlow (1976). Annotated Checklist of the Birds of Ontario. Royal Ontario Museum, ON, Canada. Close ) and mid to late May in Alberta (85 Salt, W. R. (1973). Alberta vireos and wood warblers: families Vireonidae and Parulidae, distribution and breeding. Edmonton Provincial Museum and Archives of Alberta, Edmonton, AB, Canada. Close ). Migrants were believed to reach Saskatchewan by traveling west from Manitoba (177 Smith, A. R. (1996). Atlas of Saskatchewan Birds. Saskatchewan Natural History Society Special Publications 22, Regina, SK, Canada. Close ). A similar pattern occurs in northeastern British Columbia where migrants enter the province by moving westward from northern Alberta (91 Campbell, R. W., N. K. Dawe, I. McTaggart-Cowan, J. M. Cooper, G. W. Kaiser, M. C. E. McNall and A. C. Stewart (2001). The Birds of British Columbia, Volume 4: Passerines, Wood-Warblers through Old World Sparrows. University of British Columbia Press, Vancouver, British Columbia, Canada. Close ).

The species is more rarely reported along the Gulf and Atlantic coastal plains during spring (eBird). It is also more rare in spring in western and central Pennsylvania, mainly in third and fourth weeks of May (114 Todd, W. E. C. (1940). The Birds of Western Pennsylvania. University of Pittsburgh Press, Pittsburgh, PA, USA. Close , 136 McWilliams, G. M., and D. W. Brauning (2000). The Birds of Pennsylvania. Cornell University Press, Ithaca, NY, USA. Close ), and during late May–early June in western and central New York (113 Bull, J. (1974). Birds of New York State. Doubleday Natural History Press, Garden City, NY, USA. Close ). It becomes even more rare farther east (see eBird); e.g., it is accidental in late May near Boston, Massachusetts (112 Veit, R. R., and W. R. Petersen (1993). The Birds of Massachusetts. Massachussetts Audubon Society, Lincoln, Massachusetts, USA. Close ) and a vagrant in spring in New Jersey (178 Boyle, W. J., Jr. (2011). The Birds of New Jersey: Status and Distribution. Princeton University Press, Princeton, NJ, USA. Close ).

Spring vagrants may appear to the west of the main migration range (see eBird). However, there are exceedingly few well-substantiated records in spring migration from Panama to Mexico. In Belize, there is a sighting from 9 May 2013 at Mountain Pine Ridge (179 Jones, H. L., and O. Komar (2014). Central America. North American Birds 67:525–531. Close ); it is considered a rare transient, most likely to occur on the cays in spring migration (180 Howell, S. N. G., and D. Dyer (2023). Birds of Belize. Princeton University Press, Princeton, NJ, USA. Close ). A sight report from Half Moon Cay, Belize on 7 May 1958 (181 Russell, S. M. (1964). A distributional study of the birds of British Honduras. Ornithological Monographs 1. American Ornithologists' Union, Washington, DC, USA. Close ) was later considered insufficiently described (182 Jones, H. L. (2003). Birds of Belize. University of Texas Press, Austin, TX, USA. Close ). Sight reports from Costa Rica (124 Stiles, F. G., and A. F. Skutch (1989). A Guide to the Birds of Costa Rica. Cornell University Press, Ithaca, NY, USA. Close ) were viewed to lack convincing documentation and were considered hypothetical (165 Dyer, D. and S. N. G. Howell (2023). Birds of Costa Rica. Princeton University Press, NJ, USA. Close ). Two sightings from islands off the north coast of Honduras on 17 March and 27 March in 1959 were mentioned by Monroe (183 Monroe, B. L., Jr. (1968). A distributional survey of the birds of Honduras. Ornithological Monographs 7. American Ornithologists' Union, Washington, DC, USA. Close ), but are questionable given the lack of supporting details and the early dates.

There are 6 spring records in the eastern half of Texas from 30 April to 19 May (184 Scully, M. (2011). Connecticut Warblers. San Antonio Audubon Society News 57:1–5. Close , 143 Lockwood, M. W., and B. Freeman (2014). The Texas Ornithological Society Handbook of Texas Birds. Louise Lindsey Merrick Natural Environment Series, volume 47. Texas A&M University Press, College Station, TX, USA. Close ). It is very rare in Louisiana, Arkansas, Oklahoma, and eastern Kansas from May to early June (37 Sutton, G. M. (1967). Oklahoma Birds, Their Ecology and Distribution with Comments on the Avifauna of the Southern Great Plains. University of Oklahoma Press, Norman, OK, USA. Close , eBird). It is very rare in spring in eastern Colorado (185 Andrews, P., and R. Righter (1992). Colorado Birds. Denver Museum of Natural History, Denver, Colorado, USA. Close , 186 Semo, L. S., and D. Faulkner (2011). The 57th report of the Colorado Bird Records Committee. Colorado Birds 45(1):30–41. Close , eBird), and rare in eastern Nebraska (140 Johnsgard, P. A. (2015). Birding Nebraska’s Central Platte Valley and Rainwater Basin. Zea E-Books. Book 36, University of Nebraska, Lincoln, NE, USA. Close , 187 Silcock, W. R. (2015). Spring Field Report, March 2015 to February 2015. Nebraska Bird Review 83:54–85. Close , 188 Brogie, M. A. (2016). 2015 (27th) Report of the NOU Records Committee. Nebraska Bird Review 84:138–150. Close ). Five spring records (late May and early June) were reported by Marks et al. (152 Marks, J. S., P. Hendricks, and D. Casey (2016). Birds of Montana. Buteo Books, Arrington, Virginia, USA. Close ) for Montana; one was reported from Oregon in late May (189 Rogers, T. H. (1982). Northern Rocky Mountain region. American Birds 36:875–877. Close ). It is a vagrant in California from late May to late June; records since 1958 show occurrences on Farallon Island (California), the southern Pacific Coast, and Death Valley (190 McCaskie, G. (1970). Occurrence of eastern species of Oporornis and Wilsonia in California. Condor 72:373–374. Close , 156 Garrett, K., and J. Dunn (1981). Birds of Southern California: Status and Distribution. Los Angeles Audubon Society, Los Angeles, CA, USA. Close ).

Other Migration Records

A juvenile (Formative) male was mist-netted and banded at Aldeia da Cuada, Fajãzinha on Flores Island in the Azores, Portugal in October 2019 (191 Monticelli, D., T. Valkenburg, D. Kerestúr, A. Leitão, V. Legrand, P. Alfrey, and T. Lloyd-Evans (2022). Ringing American passerines in the Azores: preliminary results with special mention of the first record of Connecticut Warbler for the Western Palearctic. British Birds 115:72–87. Close ; eBird). This record is the first one from the western Palearctic. It was one of several North American vagrants (e.g., Red-eyed Vireo (Vireo olivaceus), Swainson's Thrush (Catharus ustulatus), Common Yellowthroat (Geothlypis trichas), and American Redstart (Setophaga ruticilla)) found in the Azores following a series of low-latitude depressions and hurricane Lorenzo that year (191 Monticelli, D., T. Valkenburg, D. Kerestúr, A. Leitão, V. Legrand, P. Alfrey, and T. Lloyd-Evans (2022). Ringing American passerines in the Azores: preliminary results with special mention of the first record of Connecticut Warbler for the Western Palearctic. British Birds 115:72–87. Close ).

Fidelity to Migratory Routes and Stopover Sites

Information needed.

Movement Behavior During Stopover

Information needed.

Duration of Stopover and Migratory Periods

Hallworth et al. (64 Hallworth M. T., E. Bayne, E. McKinnon, O. Love, J. A. Tremblay, B. Drolet, J. Ibarzabal, S. Van Wilgenburg, and P. P. Marra (2021). Habitat loss on the breeding grounds is a major contributor to population declines in a long-distance migratory songbird. Proceedings of the Royal Society B 288(1949). Close ) used geolocators to follow warblers (n = 9) from four natural populations across Canada and in Minnesota and estimated stopover duration at various locations during fall migration. The average stopover on the Atlantic coast prior to transoceanic flight was 10.5 d ± 2.31 SE. The average stopover in the Caribbean or in South America was 10.7 d ± 2.43 SE (64 Hallworth M. T., E. Bayne, E. McKinnon, O. Love, J. A. Tremblay, B. Drolet, J. Ibarzabal, S. Van Wilgenburg, and P. P. Marra (2021). Habitat loss on the breeding grounds is a major contributor to population declines in a long-distance migratory songbird. Proceedings of the Royal Society B 288(1949). Close ). McKinnon et al. (128 McKinnon, E. A., C. Artuso, and O. P. Love (2017). The mystery of the missing warbler. Ecology 98:1970–1972. Close ) reported an estimate of 5‒7 days stopover in Cuba and Hispaniola.

Hallworth et al. (64 Hallworth M. T., E. Bayne, E. McKinnon, O. Love, J. A. Tremblay, B. Drolet, J. Ibarzabal, S. Van Wilgenburg, and P. P. Marra (2021). Habitat loss on the breeding grounds is a major contributor to population declines in a long-distance migratory songbird. Proceedings of the Royal Society B 288(1949). Close ) found that migrants took an average of 81.5 d ± 5.23 SE to complete fall migration from breeding to overwintering grounds.

The Connecticut Warbler is known to be hyperphagic during migration, may fatten excessively (109 Chapman, F. M. (1907). The Warblers of North America. D. Appleton & Company, New York, NY, USA. Close ), similar to other migrants where fats are made up of 16-carbon and 18-carbon fatty acids (192 McWilliams, S. R., C. Guglielmo, B. Pierce, and M. Klaassen (2004). Flying, fasting, and feeding in birds during migration: A nutritional and physiological ecology perspective. Journal of Avian Biology 35(5):377–393. Close ). There was fat deposition on the furculum and belly of a spring migrant in southern Cuba (23 León, C. P., M. P. Sánchez, Y. S. Vega, N. V. Dávila, and F. R. Santana (2019). Reporte de la Bijirita de Connecticut (Oporornis agilis; Aves: Parulidae) en el oriente de Cuba. Novitates Caribbaea 14:163–166. Close ). An adult female migrant captured in Brazil weighed 13 g, its furcular hollow filled with 30% fat (151 Diniz, C, J. D. Wolfe, M. Anciaes, and P. Stouffer (2014). New record of Connecticut Warbler Oporornis agilis in central Amazonian Brazil. Cotinga 36:127. Close ). A majority of males and females arrived on the breeding grounds in Quebec with little or no fat (27 Saulnier, M-C. (2011). Biologie de la reproduction de la Paruline à gorge grise (Oporornis agilis) dans les pinèdes grises du Lac-Saint-Jean, Canada. M.S. thesis, Université du Québec à Chicoutimi, Chicoutimi, QC, Canada. Close ). No significant differences in body mass or mass gain was found between between adult (Definitive Basic) and first-fall (First Basic) fall migrants at Long Point, Ontario (193 Jones, J., C. M. Francis, M. Drew, S. Fuller, and M. W. S. Ng (2002). Age-related differences in body mass and rates of mass gain of passerines during autumn migratory stopover. Condor 104(1):49–58. Close ). The fall vagrant from the Azores, Portugal had a body condition similar to fall migrants at Manomet Bird Observatory in eastern Massachusetts. The fat score of 3 and body mass of 14.1 g of the Azores warbler was almost identical to the mean fat score of 3 (n = 100) and mass of 14.2 g (n = 100) of Connecticut Warblers during fall migration at the Manomet Bird Observatory (191 Monticelli, D., T. Valkenburg, D. Kerestúr, A. Leitão, V. Legrand, P. Alfrey, and T. Lloyd-Evans (2022). Ringing American passerines in the Azores: preliminary results with special mention of the first record of Connecticut Warbler for the Western Palearctic. British Birds 115:72–87. Close ). Fruit made up 10% of a fecal sample obtained from one fall migrant on Block Island, Rhode Island (194 Parrish, J. D. (1997). Patterns of frugivory and energetic condition in nearctic landbirds during autumn migration. Condor 99:681–697. Close ).

La Sorte and Frank (195 La Sorte, F. A. and D. Fink (2017). Projected changes in prevailing winds for transatlantic migratory birds under global warming. Journal of Animal Ecology 86:273–284. Close ) were interested in whether climate change might affect the flight of fall migrants. They used 3 October–8 November as a time frame for the transatlantic fall migration of the Connecticut Warbler based primarily on eBird data. During this period, they found birds are currently likely to encounter winds from different directions and wind speeds at different latitudes and altitudes that could affect the transatlantic flights of these birds. Stronger westerly winds were found at more northern latitudes while easterly winds were stronger at lower latitudes. La Sorte and Fink (195 La Sorte, F. A. and D. Fink (2017). Projected changes in prevailing winds for transatlantic migratory birds under global warming. Journal of Animal Ecology 86:273–284. Close ) simulated how these winds might change as global temperatures increase. Their simulation projected a decrease in the strong westerly crosswinds at higher altitudes and latitudes where these birds begin their fall migration. They speculated that Connecticut Warbler and other species with transatlantic fall migrations could benefit from milder westerlies by expending less energy during flight and experiencing less mortality during fall migration.