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Sexual selection in birds concerns how birds have evolved a variety of mating behaviors, with the peacock tail being perhaps the most famous example of sexual selection and the Fisherian runaway. Commonly occurring sexual dimorphisms such as size and color differences are energetically costly attributes that signal competitive breeding ...
Altricial birds are less able to contribute nutrients in the pre-natal stage; their eggs are smaller and their young are still in need of much attention and protection from predators. This may be related to r/K selection; however, this association fails in some cases. [18] In birds, altricial young usually grow faster than precocial young.
When it comes to the mating behaviour of simultaneous hermaphrodites such as pulmonate land snails and pulmonate land slugs, as well as opisthobranch sea snails and opisthobranch sea slugs, there is the question of which sexual role or roles an individual will adopt in a mating encounter. [4]
Females are larger than males, and Pacific swordfish reach a greater size than northwest Atlantic and Mediterranean swordfish. [6] They reach maturity at 4–5 years of age and the maximum age is believed to be at least 9 years. [6] The oldest swordfish found in a recent study were a 16-year-old female and 12-year-old male.
Saltwater is less dilute than these internal fluids, so saltwater fish lose large quantities of water osmotically through their gills. To regain the water, they drink large amounts of seawater and excrete the salt. Freshwater is more dilute than the internal fluids of fish, however, so freshwater fish gain water osmotically through their gills ...
Bird: Bird species are typically biparental in care, and may also be maternal like the Guianan cock-of-the-rocks. However the reverse may also hold true. Male wattled jacanas provide all parental care after the eggs have been laid by the females. This means that the males must incubate the eggs and defend the nest for an extended period of time.
Roughly 70% of birds that used to be considered genetically monogamous actually engage in EPCs and raise extra-pair young (reviewed by: [48]). Furthermore, it has been proposed that birds that nest in high densities, as seabirds do in breeding colonies, have higher rates of EPCs and EPFs than birds that do not nest colonially. [46]
If this is a problem with dolphins it is an even greater problem with billfish such as swordfish, which swim and accelerate faster than dolphins. In 2009, Taiwanese researchers from the National Chung Hsing University introduced new concepts of "kidnapped airfoils and circulating horsepower" to explain the swimming capabilities of swordfish ...