Parental care in birds
Parental care refers to the level of investment provided by the mother and the father to ensure development and survival of their offspring.
In most birds, parents invest profoundly in their offspring as a mutual effort, making a majority of them socially monogamous for the duration of the breeding season.
(Michael S. Y. Lee, Andrea Cau, Darren Naish, and Gareth J. Dyke)[1] The Archaeopteryx was the first fossil bird recorded with evolved feathers.
Kavanau said extant birds (David J. Varricchio)[5] evolved and learned flight through evolution to access ground nests faster.
[7][8][9] Wesolowsi (1994) contradicted Kavanau's reasoning by saying flight evolved due to parental care not reproduction as previously thought.
While flight was being enhanced in evolutionary stages, lack of parental care meant that the increasing number of large eggs required a higher level of investment.
This created young that were able to take flight shortly after hatching which is known as precocial, in the form of unassisted paternal (male only) care.
The good parent hypothesis states that birds can invest more energy towards their own survival rate by choosing an ideal mate.
Evolution in potential mates to advertise their parental strengths through ornamental cues (e.g. a yellow chest patch in Iberian rock sparrows) are based on the differential allocation hypothesis.
(Andrew Cockburn)[14] A hypothesis states that the parent that invests less reproductive effort in comparison to its mate, will have a higher chance of deserting because it loses less if successful offspring are not produced.
However, in some birds (such as the snail kite found in South America, the Caribbean and Florida), the male and the female sometimes compete over which one will desert the nest regardless of which one has invested more into the reproductive effort.
Parental roles also cause a reverse in phenotypic differentiation (genetics) resulting in more colorful and larger females compared with males.
Species which exhibit this behavior include certain types of red and red-necked phalaropes, and spotted sandpipers which breed in South America.
(Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye)[17] The male to female ratio has an effect on the type and amount of care provided.
[further explanation needed] Visser et al. (2009) has attempted to find this connection with a 6-year-long experiment in great tits (Parus major).
David Lack (1958)[20] The brood size (number of eggs laid per clutch) is another factor which effects quality and survival rate.
Williams (1966)[21] If there is a higher level of feeding in birds such as the collared flycatchers (Ficedula albicollis), then there is an increase in parental investment during the mating season.
(Gustafsson & Sutherland, 1988) The cause might be that effort reserved for reproduction is diminished by a need to maintain the immune system this leads to a physiological condition hindering breeding.
(Sheldon & Verhulst, 1996; Norris & Evans, 2000) In most bird species, females invest in parental care more than males at the expense of reproductive success.
A hypothesis was tested in South America to see if species of birds would respond more aggressively to an adult predator (a hawk) than their Northern counterparts because they care more about future reproductive success due to a smaller brood size.
The experiment showed that those fed the sugary solution had an increased chance to create an additional future clutch during the same mating season.
(Rose Thorogood and colleagues (2011))[22] In black-backed gull (Larus fuscus) females which were supplementally fed and had higher body condition produced eggs with a lower level of androgens (such as testosterone).
Though themselves associated with tradeoffs, yolk steroids may help compensate for hostile conditions and serve as a prenatal form of parental investment.
Upon hatching, the young chick starts to create his own IgY but the mothers antibodies will still influence development and growth rate.
These same antioxidants also prevent the destruction of maternal antibodies (IgY) which are extremely important to survival rate and can be seen as a form of pre-birth parental care.
[clarification needed] (Gavin H. Thomas, Tamás Székely)[28] There is a positive correlation between ornamental cues and the parental care invested in Iberian rock sparrows (Vincente Garcia-Navas).
(Rikón, Amanda Garcia Del)[29] Two pair species of common yellowthroats were analyzed from Wisconsin and New York for the effect of ornamental cues on parental care.
Males possess a black face mask and yellow (breast, throat, and belly) patch which is usually completely absent in females.
In both U.S. states, yellowthroat males with a larger patch had a lower parental investment towards their young however the ornament involved varied.
The trade-off hypothesis matches the results which says larger ornamental cues on males leads to less parental investment because their effort is diverted to finding more mates for future reproductive success or holding on to territories.
