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Wader

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Title: Wader  
Author: World Heritage Encyclopedia
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Subject: Picture of the day/March 2013, Hunter Estuary Wetlands, Cursorius, Spittal Pond Nature Reserve, Crab-plover
Collection: Charadrii, Chionidi, Shorebirds, Thinocori
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Wader

Waders
Temporal range: Late Oligocene to recent
Semipalmated sandpiper (Calidris pusilla)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes (partim)
Suborders

Waders, called shorebirds in North America (where "wader" is used to refer to long-legged wading birds such as storks and herons), are members of the order Charadriiformes, excluding the more marine web-footed seabird groups.

There are about 210 species, most of which are associated with wetland or coastal environments. Many species of Arctic and temperate regions are strongly migratory, but tropical birds are often resident, or move only in response to rainfall patterns. Some of the Arctic species, such as little stint, are amongst the longest distance migrants, spending the non-breeding season in the southern hemisphere.

Many of the smaller species found in coastal habitats, particularly but not exclusively the calidrids, are often named as "sandpipers", but this term does not have a strict meaning, since the upland sandpiper is a grassland species.

The smallest member of this group is the least sandpiper, small adults of which can weigh as little as 15.5 grams and measure just over 13 cm (5.1 in). The largest species is believed to be the Far Eastern curlew, at about 63 cm (25 in) and 860 grams (1.90 pounds), although the beach thick-knee is the heaviest at about 1 kg (2.2 lb).

In the Sibley-Ahlquist taxonomy, waders and many other groups are subsumed into a greatly enlarged Ciconiiformes order. However, the classification of the Charadriiformes is one of the weakest points of the Sibley-Ahlquist taxonomy, as DNA-DNA hybridization has turned out to be incapable of properly resolving the interrelationships of the group. Formerly, the waders were united in a single suborder Charadrii, but this has turned out to be a "wastebasket taxon", uniting no less than four charadriiform lineages in a paraphyletic assemblage. However, it indicated that the plains wanderer actually belonged into one of them. Following recent studies (Ericson et al., 2003; Paton et al., 2003; Thomas et al., 2004a, b; van Tuinen et al., 2004; Paton & Baker, 2006), the waders may be more accurately subdivided as follows:

In keeping more in line with the traditional grouping, the Thinocori could be included in the Scolopaci, and the Chionidi in the Charadrii. However, the increasing knowledge about the early evolutionary history of modern birds suggests that the assumption of Paton et al. (2003) and Thomas et al. (2004b) of 4 distinct "wader" lineages (= suborders) already being present around the Cretaceous–Paleogene boundary is correct.

Contents

  • Characteristics 1
    • Sexual Dimorphism 1.1
  • See also 2
  • References 3
  • Sources 4

Characteristics

Shorebirds is a blanket term used to refer to multiple species of birds that live in wet, coastal environments. Because most these species spend much of their time near bodies of water, many have long legs suitable for wading (hence the name ‘Waders’). Some species prefer locations with rocks or mud. Many shorebirds display migratory patterns and often migrate before breeding season. These behaviors explain the long wing lengths observed in species, and can also account for the efficient metabolisms that give the birds energy during long migrations.

The majority of species eat small invertebrates picked out of mud or exposed soil. Different lengths of bills enable different species to feed in the same habitat, particularly on the coast, without direct competition for food. Many waders have sensitive nerve endings at the end of their bills which enable them to detect prey items hidden in mud or soft soil. Some larger species, particularly those adapted to drier habitats will take larger prey including insects and small reptiles.

Sexual Dimorphism

Shorebirds, like many other animals, exhibit phenotypic differences between males and females, also known as sexual dimorphism. One of the biggest factors that led to the development of sexual dimorphism in shorebirds is sexual selection. Males with ideal characteristics chosen by females will be able to reproduce and pass on their genetic information to their offspring. If individuals from the shorebird species are in situations where apparent sexual selection will determine reproductive success, the individuals who display significantly different physical features from their female counterparts will be favored.[1]

Dimorphisms vary greatly in polygamous species, where male individuals mate with multiple female partners. Competition between males tends to lead to sexual preference of larger males who could appeal to female counterparts by defeating other male competitors. Similarly, birds who use courtship displays may be chosen as mates if they have high airborne acrobatics skills. In monogamous species, where male individuals mate with a single female partner, males typically do not to have such distinct features such as colored feathers, but they still tend to be larger in size compared to females.

The suborder of Charadrii displays the widest range of sexual dimorphisms seen in the Charadriiformes order.[2] Cases of sexual monomorphism, where there are no distinguishing physical features besides external genitalia, are even seen in this order.

See also

References

  1. ^ Szekely, T., R. P. Freckleton, and J. D. Reynolds. "Sexual Selection Explains Rensch's Rule of Size Dimorphism in Shorebirds." Proceedings of the National Academy of Sciences (2004): 12224-2227. Print.
  2. ^ * Székely, Tamás, John D. Reynolds, and Jordi Figuerola. 2000. Sexual Size Dimorphism In Shorebirds, Gulls, And Alcids: The Influence Of Sexual And Natural Selection. 54(4): 1404-413. [2]

Sources

  • Ericson, P. G. P.; Envall, I.; Irestedt, M. & Norman, J. A. (2003). Inter-familial relationships of the shorebirds (Aves: Charadriiformes) based on nuclear DNA sequence data. BMC Evol. Biol. 3: 16. doi:10.1186/1471-2148-3-16 PDF fulltext
  • Paton, Tara A. & Baker, Allan J. (2006). Sequences from 14 mitochondrial genes provide a well-supported phylogeny of the Charadriiform birds congruent with the nuclear RAG-1 tree. Molecular Phylogenetics and Evolution 39(3): 657–667. doi:10.1016/j.ympev.2006.01.011 PMID 16531074 (HTML abstract)
  • Paton, T. A.; Baker, A. J.; Groth, J. G. & Barrowclough, G. F. (2003). RAG-1 sequences resolve phylogenetic relationships within charadriiform birds. Molecular Phylogenetics and Evolution 29: 268-278. doi:10.1016/S1055-7903(03)00098-8 PMID 13678682 (HTML abstract)
  • Thomas, Gavin H.; Wills, Matthew A. & Székely, Tamás (2004a). Phylogeny of shorebirds, gulls, and alcids (Aves: Charadrii) from the cytochrome-b gene: parsimony, Bayesian inference, minimum evolution, and quartet puzzling. Molecular Phylogenetics and Evolution 30(3): 516-526. doi:10.1016/S1055-7903(03)00222-7 (HTML abstract)
  • Thomas, Gavin H.; Wills, Matthew A. & Székely, Tamás (2004b). A supertree approach to shorebird phylogeny. BMC Evol. Biol. 4: 28. doi:10.1186/1471-2148-4-28 PMID 15329156 PDF fulltext Supplementary Material
  • van Tuinen, Marcel; Waterhouse, David & Dyke, Gareth J. (2004). Avian molecular systematics on the rebound: a fresh look at modern shorebird phylogenetic relationships. Journal of Avian Biology 35(3): 191-194. PDF fulltext
  • Explore the World With Shorebirds. (2004). U.S. Fish and Wildlife Service. Web. .
  • Lindenfors, P., T. Szekely, and J. D. Reynolds. (2003). Directional Changes in Sexual Size Dimorphism in Shorebirds, Gulls and Alcids. Journal of Evolutionary Biology J Evolution Biol: 930-38. Print.
  • Szekely, T.,Freckleton, R., & Reynolds, J. (2004). Sexual selection explains Rensch's rule of size dimorphism in shorebirds. Proceedings of the National Academy of Sciences. 101(33): 12224-12227.
  • Szekely, Tamas, John D. Reynolds, and Jordi Figuerola. (2000) Sexual Size Dimorphism in Shorebirds, Gulls, and Alcids: The Influence of Sexual and Natural Selection. Evolution 54(4): 1404-413.
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