Lecture_20 - green What might egg color indicate EASTERN...

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Lecture 20 Notes Maternal effects…continued. Aside from sex ratio and egg content, females can also vary: 1.) Egg size Largest living bird egg = ostrich Largest bird egg = elephantbird Smallest bird egg = hummingbird Generally, larger birds lay larger eggs, but larger birds lay eggs that are a smaller percentage of their body weight. 2.) Egg shape Range from pyroform (pointed) oval spherical Depends on muscular tension and diameter of oviduct 3.) Egg patterns – vary based on pigmentation pattern 4.) Egg color Color varies among species Also varies among individuals within a species Egg color spectrum is generally created through a combination of three main colors: White – produced by calcium carbonate Brown – produced by protoporphyrin Blue – produced by biliverdin In poultry, egg color depends on genetics: Oocyan – dominant gene on chromosome 1 blue eggs
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Brown results from interactions of multiple genes Oocyan gene + brown multigene background
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Unformatted text preview: green What might egg color indicate? EASTERN BLUEBIRD EXAMPLE PIED FLYCATCHER EXAMPLE SPOTLESS STARLING EXAMPLE How might eggshell color function? a. Indicate investment by female? b. Provide fortification or protection for offspring? c. Helps to discriminate eggs from brood parasites? d. Affects paternal care? Functions of brown speckles? a. Mimicry? b. Crypsis? c. Egg strengtheners? GREAT TIT EXAMPLE 5.) Clutch Size Two general strategies: Fixed – always the same number of eggs Variable – can change clutch size What determines clutch size? Parental ability Risk of loss Phylogeny Once again, we have a cost-benefit ratio. Factors affecting clutch sizes: Ecological effects – territory size, prey availability Latitude Ashmole’s Hypothesis – Because there is higher food availability at higher latitudes during breeding times, females can invest more in reproduction at higher latitudes = larger clutch sizes....
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