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Saltmarsh sparrow

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The saltmarsh sparrow (Ammospiza caudacuta) is a small New World sparrow found in salt marshes along the Atlantic coast of the United States. At one time, this bird and the Nelson's sparrow (Ammospiza nelsoni) were thought to be a single species, the sharp-tailed sparrow. Because of this, the species was briefly known as the "saltmarsh sharp-tailed sparrow." Saltmarsh sparrow numbers are declining due to habitat loss largely attributed to human activity.

Saltmarsh sparrow

Imperiled  (NatureServe)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Passerellidae
Genus: Ammospiza
Species:
A. caudacuta
Binomial name
Ammospiza caudacuta
(Gmelin, JF, 1788)
Subspecies
  • Ammospiza caudacuta caudacuta (J. F. Gmelin, 1788)
  • Ammospiza caudacuta diversa (Bishop, 1901)
  Breeding
  Year-round
  Non-Breeding
Synonyms[3]
  • Ammodramus caudacutus (J. F. Gmelin, 1788)

Taxonomy

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The saltmarsh sparrow was formally described in 1788 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the orioles in the genus Oriolus and coined the binomial name Oriolus caudacutus. He gave the locality as New York.[4] Gmelin based his own description on those for the "sharp-tailed oriole" that had been described by John Latham in 1782 and by Thomas Pennant in 1785.[5][6] The saltmarsh sparrow is now one of four American sparrows placed in the genus Ammospiza that was introduced by Harry C. Oberholser in 1905.[7] The genus name combines the Ancient Greek αμμος (ammos) meaning "sand" and σπιζα (spiza) meaning "finch". The specific epithet caudacuta is from Latin cauda meaning "tail" and acutus meaning "sharp".[8]

Its closest relatives are the Nelson's sparrow (Ammospiza nelsoni) and the seaside sparrow (Ammospiza maritima).[9][10]

Two subspecies are recognised:[7]

  • A. c. caudacuta (Gmelin, JF, 1788) – breeding northeast USA
  • A. c. diversa (Bishop, 1901) – breeding east USA

The saltmarsh sparrow and the Nelson's sparrow were once thought to be a single species, called the sharp-tailed sparrow. Mitochondrial DNA evidence suggests that the two species diverged about 600,000 years ago.[11] A Pleistocene glaciation is thought to have separated the ancestral sharp-tailed sparrow into inland and coastal populations. The inland Nelson's sparrow became a specialist of non-tidal freshwater wetlands while the coastal saltmarsh sparrow became a specialist of tidal salt marshes.[12] Recently, the Nelson's sparrow has expanded its range to include coastal salt marshes, and interbreeding occurs where the two species overlap.[13][14]

Description

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The saltmarsh sparrow measures 11–14 cm (4.3–5.5 in) in length, has a wingspan of 17.8–21 cm (7.0–8.3 in), and weighs 14–23.1 g (0.49–0.81 oz).[15][16] Adults have brownish upperparts with a gray nape, white throat and belly, and pale orange breast and sides with brown streaking. The face is orange with gray cheeks, a gray median crown stripe, brown lateral crown stripes, and a brown eyeline. The tail feathers are short and sharply pointed.[17] The subspecies A. c. diversa has more contrasting striping on its back and a darker crown than the nominate A. c. caudacuta.[18]

Only males sing.[19] The song is a complex series of raspy, barely audible buzzes, trills, and gurgles. It is distinguishable from that of the Nelson's sparrow, which is a louder, hissing buzz followed by a buzzy chip. The high-pitched contact calls of both species are indistinguishable.[17]

Distinguishing this species from closely related sparrows such as the Nelson's sparrow (Ammospiza nelsoni) can be difficult. The inland subspecies of the Nelson's sparrow can be differentiated by its fainter streaking and brighter orange breast and sides, while the coastal subspecies of the Nelson's sparrow can be differentiated by its paler, less-contrasting plumage. The saltmarsh sparrow also has a slightly longer beak than the Nelson's sparrow.[17]

Distribution and habitat

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The saltmarsh sparrow is only found in tidal salt marshes along the Atlantic coast of the United States. It breeds along the northern coast, from Maine to the Chesapeake Bay, and winters along the southern coast, from North Carolina to Florida.[19] The saltmarsh sparrow prefers high marsh habitat, dominated by saltmeadow cordgrass (Sporobolus pumilus) and saltmarsh rush (Juncus gerardii), which does not flood as frequently as low marsh.[20]

Behavior

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Diet

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The saltmarsh sparrow forages on the ground along tidal channels or in marsh vegetation, sometimes probing in the mud at low tide. Over 80% of the diet of nestlings consists of flies, amphipods, grasshoppers, and moths, especially larval, pupal, and adult soldier flies.[21] During the winter, adults consume seeds.[19] The saltmarsh sparrow is an opportunistic feeder and food is rarely limiting.[21]

Breeding

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A newly hatched saltmarsh sparrow and eggs in nest
 
Saltmarsh sparrow chick

Saltmarsh sparrows are non-territorial and have large overlapping home ranges. Male home ranges are twice as large as those of females and may span 50 hectares (120 acres).[22] Saltmarsh sparrows are promiscuous, and the majority of broods exhibit mixed parentage.[23] During the nesting season, males roam long distances chasing and mounting females regardless of receptivity. Only females exhibit parental care, building the nest, incubating the eggs, and providing food to the young.[12] The nest is an open cup constructed of grass, usually attached to saltmeadow cordgrass (Sporobolus pumilus) or saltmarsh rush (Juncus gerardii) at a height of 6–15 centimetres (2.4–5.9 in). Clutch size is 3 to 5. Incubation begins after the last egg is laid and takes 11–12 days. Young fledge 8–11 days after hatching but remain dependent on the mother for an additional 15–20 days.[19]

The primary cause of nest mortality is flooding due to storm surges and periodic, exceptionally high spring tides which occur every 28 days during the new moon. The saltmarsh sparrow exhibits several adaptations to flooding, including nest repair, egg retrieval, rapid re-nesting, and synchronization of breeding with the lunar cycle.[24][25] Nesting begins immediately following a spring tide, allowing young to fledge before the next spring tide.[25] Two broods are typically raised per breeding season.[19]

Conservation status

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The saltmarsh sparrow is of high conservation concern due to habitat loss resulting in small fragmented populations.[19][26] Salt marshes are one of the most threatened habitats worldwide due to their limited natural extent, long history of human modification, and anticipated sea level rise.[27] The spread of the invasive reed Phragmites has also contributed to habitat loss.[28] The saltmarsh sparrow is very sensitive to sea level rise because of the role of flooding in nest mortality.[29] In addition, the saltmarsh sparrow is particularly susceptible to mercury bioaccumulation, but the effects of this on survival are unclear.[30][31][32]

Saltmarsh sparrow populations declined between 5% and 9% per year between the 1990s and 2010s, resulting in a total decline of over 75%.[19][33] Without management intervention, the saltmarsh sparrow is projected to become extinct by 2050.[19] The saltmarsh sparrow was listed on the 2016 State of North America's Birds Watch List with a concern score of 19 out of 20,[34] and the U.S. Fish and Wildlife Service is currently undertaking a status review to determine whether the species should be listed under the Endangered Species Act.[35][36] Its total population was estimated to be 53,000 in 2016.[37]

References

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  1. ^ BirdLife International (2020). "Ammospiza caudacuta". IUCN Red List of Threatened Species. 2020: e.T22721129A180407945. doi:10.2305/IUCN.UK.2020-3.RLTS.T22721129A180407945.en. Retrieved 23 February 2023.
  2. ^ "NatureServe Explorer 2.0". explorer.natureserve.org. Retrieved 10 November 2022.
  3. ^ "Ammospiza caudacuta (J. F. Gmelin, 1788)". Integrated Taxonomic Information System. Retrieved 23 February 2023.
  4. ^ Gmelin, Johann Friedrich (1788). Systema naturae per regna tria naturae : secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis (in Latin). Vol. 1, Part 1 (13th ed.). Lipsiae [Leipzig]: Georg. Emanuel. Beer. p. 394.
  5. ^ Latham, John (1782). A General Synopsis of Birds. Vol. 1, Part 2. London: Printed for Benj. White. p. 448, Plate 17.
  6. ^ Pennant, Thomas (1785). Arctic Zoology. Vol. 2. London: Printed by Henry Hughs. pp. 261–262, n. 152.
  7. ^ a b Gill, Frank; Donsker, David; Rasmussen, Pamela, eds. (July 2023). "New World Sparrows, Bush Tanagers". IOC World Bird List Version 13.2. International Ornithologists' Union. Retrieved 14 November 2023.
  8. ^ Jobling, James A. (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. pp. 45, 94. ISBN 978-1-4081-2501-4.
  9. ^ Robins, Jerome D.; Schnell, Gary D. (1971). "Skeletal Analysis of the Ammodramus-ammospiza Grassland Sparrow Complex: A Numerical Taxonomic Study". The Auk. 88 (3): 567–590. JSTOR 4083751.
  10. ^ Zink, Robert M.; Avise, John C. (1990-06-01). "Patterns of Mitochondrial DNA and Allozyme Evolution in the Avian Genus Ammodramus". Systematic Zoology. 39 (2): 148–161. doi:10.2307/2992452. ISSN 1063-5157. JSTOR 2992452. S2CID 86467120.
  11. ^ Rising, James D.; Avise, John C. (1993). "Application of Genealogical-Concordance Principles to the Taxonomy and Evolutionary History of the Sharp-Tailed Sparrow (Ammodramus caudacutus)". The Auk. 110 (4): 844–856. doi:10.2307/4088638. JSTOR 4088638. S2CID 22137914.
  12. ^ a b Greenlaw, Jon S. (1993). "Behavioral and Morphological Diversification in Sharp-Tailed Sparrows (Ammodramus caudacutus) of the Atlantic Coast". The Auk. 110 (2): 286–303. JSTOR 4088557.
  13. ^ Shriver, W. Gregory; Gibbs, James P.; Vickery, Peter D.; Gibbs, H. Lisle; Hodgman, Thomas P.; Jones, Peter T.; Jacques, Christopher N.; Fleischer, R. C. (2005-01-01). "Concordance between morphological and molecular markers in assessing hybridization between sharp-tailed sparrows in New England". The Auk. 122 (1): 94–107. doi:10.1642/0004-8038(2005)122[0094:CBMAMM]2.0.CO;2. ISSN 0004-8038. S2CID 3736684.
  14. ^ Walsh, Jennifer; Kovach, Adrienne I.; Lane, Oksana P.; O'Brien, Kathleen M.; Babbitt, Kimberly J. (2011-05-19). "Genetic Barcode RFLP Analysis of the Nelson's and Saltmarsh Sparrow Hybrid Zone". The Wilson Journal of Ornithology. 123 (2): 316–322. doi:10.1676/10-134.1. ISSN 1559-4491. S2CID 86551697.
  15. ^ "Saltmarsh Sparrow, Life History, All About Birds - Cornell Lab of Ornithology". Allaboutbirds.org. Retrieved 2013-02-18.
  16. ^ CRC Handbook of Avian Body Masses by John B. Dunning Jr. (Editor). CRC Press (1992), ISBN 978-0849342585.
  17. ^ a b c Sibley, David (2003). The Sibley field guide to birds of eastern North America (1st ed.). New York: Alfred A. Knopf. ISBN 9780679451204. OCLC 52075784.
  18. ^ Smith, Fletcher M. (2011). "Photo Essay: Subspecies of Saltmarsh Sparrow and Nelson's Sparrow" (PDF). North American Birds. 65 (2): 368–377.
  19. ^ a b c d e f g h GREENLAW, JON S.; RISING, JAMES D. (1994). "Saltmarsh Sharp-tailed Sparrow (Ammodramus caudacutus)". The Birds of North America Online. doi:10.2173/bna.112.
  20. ^ Greenlaw, Jon S.; Woolfenden, Glen E. (2007-09-01). "Wintering distributions and migration of saltmarsh and Nelson's sharp-tailed sparrows". The Wilson Journal of Ornithology. 119 (3): 361–377. doi:10.1676/05-152.1. ISSN 1559-4491. S2CID 85846189.
  21. ^ a b Post, William; Greenlaw, Jon S. (2006-10-01). "Nestling diets of coexisting salt marsh sparrows: Opportunism in a food-rich environment". Estuaries and Coasts. 29 (5): 765–775. Bibcode:2006EstCo..29..765P. doi:10.1007/BF02786527. ISSN 1559-2723. S2CID 84064446.
  22. ^ Shriver, W. Gregory; Hodgman, Thomas P.; Gibbs, James P.; Vickery, Peter D. (2010-05-12). "Home Range Sizes and Habitat Use of Nelson's and Saltmarsh Sparrows". The Wilson Journal of Ornithology. 122 (2): 340–345. doi:10.1676/09-149.1. ISSN 1559-4491. S2CID 85887167.
  23. ^ Hill, Christopher E.; Gjerdrum, Carina; Elphick, Chris S. (2010-04-01). "Extreme Levels of Multiple Mating Characterize the Mating System of the Saltmarsh Sparrow (Ammodramus caudacutus)". The Auk. 127 (2): 300–307. doi:10.1525/auk.2009.09055. ISSN 0004-8038. S2CID 11340274.
  24. ^ Gjerdrum, Carina; Elphick, Chris S.; Rubega, Margaret (2005-11-01). "Nest site selection and nesting success in saltmarsh breeding sparrows: the importance of nest habitat, timing, and study site differences". The Condor. 107 (4): 849–862. doi:10.1650/7723.1. ISSN 0010-5422. S2CID 86061445.
  25. ^ a b Shriver, W. Gregory; Vickery, Peter D.; Hodgman, Thomas P.; Gibbs, James P.; Sandercock, B. K. (2007-04-01). "Flood tides affect breeding ecology of two sympatric sharp-tailed sparrows". The Auk. 124 (2): 552–560. doi:10.1642/0004-8038(2007)124[552:FTABEO]2.0.CO;2. ISSN 0004-8038. S2CID 86291773.
  26. ^ DiQuinzio, Deborah A.; Paton, Peter W. C.; Eddleman, William R.; Brawn, J. (2001-10-01). "Site fidelity, philopatry, and survival of promiscuous saltmarsh sharp-tailed sparrows in Rhode Island". The Auk. 118 (4): 888–899. doi:10.1642/0004-8038(2001)118[0888:SFPASO]2.0.CO;2. ISSN 0004-8038. S2CID 45574106.
  27. ^ Gedan, K. Bromberg; Silliman, B. R.; Bertness, M. D. (2009). "Centuries of Human-Driven Change in Salt Marsh Ecosystems". Annual Review of Marine Science. 1 (1): 117–141. Bibcode:2009ARMS....1..117G. CiteSeerX 10.1.1.319.6842. doi:10.1146/annurev.marine.010908.163930. PMID 21141032.
  28. ^ Benoit, Lori K.; Askins, Robert A. (1999-03-01). "Impact of the spread of Phragmites on the distribution of birds in Connecticut tidal marshes". Wetlands. 19 (1): 194–208. Bibcode:1999Wetl...19..194B. doi:10.1007/BF03161749. ISSN 0277-5212. S2CID 24161204.
  29. ^ Bayard, Trina S.; Elphick, Chris S. (2011-04-01). "Planning for Sea-Level Rise: Quantifying Patterns of Saltmarsh Sparrow (Ammodramus caudacutus) Nest Flooding Under Current Sea-Level Conditions". The Auk. 128 (2): 393–403. doi:10.1525/auk.2011.10178. ISSN 0004-8038. S2CID 86661955.
  30. ^ Lane, Oksana P.; O’Brien, Kathleen M.; Evers, David C.; Hodgman, Thomas P.; Major, Andrew; Pau, Nancy; Ducey, Mark J.; Taylor, Robert; Perry, Deborah (2011-11-01). "Mercury in breeding saltmarsh sparrows (Ammodramus caudacutus caudacutus)". Ecotoxicology. 20 (8): 1984–91. Bibcode:2011Ecotx..20.1984L. doi:10.1007/s10646-011-0740-z. ISSN 0963-9292. PMID 21792662. S2CID 15429827.
  31. ^ Cristol, Daniel A.; Smith, Fletcher M.; Varian-Ramos, Claire W.; Watts, Bryan D. (2011-11-01). "Mercury levels of Nelson's and saltmarsh sparrows at wintering grounds in Virginia, USA". Ecotoxicology. 20 (8): 1773–1779. Bibcode:2011Ecotx..20.1773C. doi:10.1007/s10646-011-0710-5. ISSN 0963-9292. PMID 21698442. S2CID 21720566.
  32. ^ Winder, Virginia L. (2012-09-04). "Characterization of Mercury and Its Risk in Nelson's, Saltmarsh, and Seaside Sparrows". PLOS ONE. 7 (9): e44446. Bibcode:2012PLoSO...744446W. doi:10.1371/journal.pone.0044446. ISSN 1932-6203. PMC 3433451. PMID 22962614.
  33. ^ Shriver, W. Gregory; O’Brien, Kathleen M.; Ducey, Mark J.; Hodgman, Thomas P. (2016-01-01). "Population abundance and trends of Saltmarsh (Ammodramus caudacutus) and Nelson's (A. nelsoni) Sparrows: influence of sea levels and precipitation". Journal of Ornithology. 157 (1): 189–200. doi:10.1007/s10336-015-1266-6. ISSN 2193-7192. S2CID 17586419.
  34. ^ "Species Assessment Summary and Watch List". State of North America's Birds 2016. Retrieved 2017-10-02.
  35. ^ "Saltmarsh Sparrow". U.S. Fish & Wildlife Service. Retrieved 23 February 2023.
  36. ^ Gifford, Krishna (2019). "Saltmarsh Sparrow (Ammospiza caudacuta) Peer Review Plan". U.S. Fish and Wildlife Service. Retrieved 23 February 2023.
  37. ^ Wiest, Whitney A.; Correll, Maureen D.; Olsen, Brian J.; Elphick, Chris S.; Hodgman, Thomas P.; Curson, David R.; Shriver, W. Gregory (2016-03-16). "Population estimates for tidal marsh birds of high conservation concern in the northeastern USA from a design-based survey". The Condor. 118 (2): 274–288. doi:10.1650/CONDOR-15-30.1. ISSN 0010-5422.
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