The "'dusky seaside sparrow "', " Ammodramus maritimus nigrescens ", was a non-migratory subspecies of the seaside sparrow, found in Florida in the natural salt marshes of Merritt Island and along the St . Johns River.
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One of the numerous subspecies of this bird, the dusky seaside sparrow ( " A . m . nigrescens " ), has recently become extinct, and the Cape Sable subspecies, " A . m . mirabilis ", is endangered.
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There are few well-documented occurrences of " B . pila " outside North America . " B . pila " closely resembles the European " B . nigrescens ", from which it can be reliably distinguished only by microscopic characteristics.
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The numbers of " C . nigrescens " can vary dramatically from year to year, for reasons that are unclear ( probably due to a varying rates of seedling germination and survival ), but the underlying trend seems stable, and there has been no change in its distribution.
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In 2015, Ashlee Shipham and colleagues published a molecular study based on nuclear DNA finding that " P . venustus " and " P . adscitus " were sister species, and that " P . elegans nigrescens " diverged earlier than " P . caledonicus ".
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Of the twelve species only 4 are known to reach sizes in excess of 10 lbs . two Atlantic Ocean species ( " Centropomus undecimalis " and " Centropomus poeyi " ) and two Pacific Ocean species ( " Centropomus viridis " and " Centropomus nigrescens " ).
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There is also a higher diversity of species in the hardveld compared with the sandveld . " Peltophorum africanum ", " Acacia nigrescens ", " A . tortilis ", " Combretum apiculatum " and " Colophospermum mopane " are some of the representative species of the northern hardveld.
28.
The nominate subspecies " S . n . nigrescens " occurs on the Pacific coastal region from British Columbia to northern California, while " S . n . halseii ", described by Giraud in 1841, occupies the inland parts of its range . " S . n . halseii " birds are slightly larger and more gray in their upperparts.
