Lecture22 - BioNB 2210 Lecture 22 Oct 17 2011 Lecture 22 Families I Cooperative Breeding Dr Walt Koenig Main learning objectives a Brief review of

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Unformatted text preview: BioNB 2210: Lecture 22 Oct. 17, 2011 Lecture 22: Families I: Cooperative Breeding Dr. Walt Koenig Main learning objectives: a) Brief review of mating systems b) Learn about the diversity of cooperative breeding and some of the more important questions raised by cooperative breeding systems c) Learn about the world’s most interesting bird, the acorn woodpecker 1) Review of social mating systems: a) Monogamy (usually, but not always,1 male + 1 female) Examples: mute swans, oystercatches, California mouse, humans b) Polygamy 1. Polygyny (1 male mated to multiple females) Examples: red-winged blackbirds, bobolinks 2. Polyandry (1 female mated to multiple males) Examples: Phalaropes, jacanas, spotted sandpipers 3. Polygynandry (multiple males mated to multiple females) Examples: dunnocks, Smith’s longspurs, acorn woodpeckers c) Promiscuity (no lasting pair bond) Examples: birds of paradise, sage grouse, Andean cock-of-the-rock Caveat: the genetic mating system may or may not coincide with the social mating system! Why? Extra-pair paternity (EPFs)! Example of no EPFs: Florida scrub-jay (genetic = social mating system) Examples of intermediate levels of EPFs: chickadees, western bluebirds Example of very high rates of EPFs: superb fairy-wren (Australia) 2) Studying mating systems a) Need to follow individuals! (But how?) b) Historical footnote: color-banding birds and Margaret Morse Nice c) The importance of genetic relatedness: W. D. Hamilton and kin selection 3) Cooperative breeding a) Defining feature: more than two individuals caring for young b) Typically: young remain with parents for an extended period of time (these are family-based systems) c) Usually not common, but found with all the above mating types (except promiscuity) BioNB 2210: Lecture 22 Oct. 17, 2011 4) Examples of cooperative breeders and why they are interesting to behavioral ecologists a) Importance of ecological constraints and alternative strategies (Red-cockaded woodpeckers) 1. Male ‘helpers-at-the-nest’ common 2. Why? Apparently related to the unusual nest cavities and the protection they afford against snake predation (see photo) Nest cavities appear to be a key ecological constraint driving delayed dispersal 3. Comparison of ‘stay and foray’ vs. ‘depart and search’ strategies The two strategies are comparable in terms of their fitness benefits. b) A key ecological constraint: habitat saturation (Seychelles warblers) 1. Transplanted to new island! 2. Became a cooperative breeder (helpers) once the birds became sufficiently numerous that they ‘filled up’ the available territories (see figure) An example of habitat saturation driving delayed dispersal and cooperative breeding c) Helping is often ‘making the best of a bad job’ (Florida scrub-jays) 1. Socially and genetically monogamous 2. Fledglings typically delay dispersal and help 3. Fitness comparison of helping vs. breeding Delay dispersal and help: Young produced by experienced pairs w/o help Young produced by experienced pairs WITH help Extra young due to helpers Mean fitness of a helper (r = 0.5) 1.80 2.38 0.58 0.29 BioNB 2210: Lecture 22 Oct. 17, 2011 Disperse and breed Young produced by first-time breeders Mean fitness of a first-time breeder (r = 0.5) 1.24 0.62 4. Conclusion: breeding is better than helping! So why do young delay dispersal and help? 5. Do helpers really help? They appear to based on the above fitness comparison, but what if pairs with helpers do better not because of the helpers but because they live on higher-quality territories than pairs without helpers? a. Test experimentally with helper removals b. Results: not much of a difference in terms of young fledged, but survivorship of young much higher in control groups compared to those in which helpers were removed (see figure) c. Conclusion: helpers do help, but not necessarily in ways that one might expect! d. The unresolved mystery of why some taxa are cooperative breeders and others are not (the distribution of scrub-jay genus Aphelocoma) 1. Disjunct population in Florida (cooperative breeders) 2. Western populations NOT cooperative breeders (with one exception) 3. Disjunct population on Santa Cruz Island are not cooperative breeders (even though they appear to live under conditions of strong ecological constraints!) 4. Most southern population of the western scrub-jay in Oaxaca exhibit evidence of being cooperative breeders! 5. Evidence suggests that cooperative breeding is the ancestral state in this taxon! What factors drive some of these to be cooperative breeders and others not? Why are there so many cooperative breeders in Australia? BioNB 2210: Lecture 22 Oct. 17, 2011 ...
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This note was uploaded on 08/27/2011 for the course BIONB 2210 taught by Professor Seeley during the Fall '10 term at Cornell University (Engineering School).

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