(Brown 1964)
Brandt’s Cormorants
Defend nest site on cliff
Do not defend feeding sites at sea
Sage grouse food is
Not limited, nor defended
Nest is not defended as that might increase detection by predators
No defensible resource allows leks to form
Food and space to breed are defensible in most songbirds, so all purpose territories evolve

• Diversity
– Polyandry, Polygyny, Polygynandry, and Monogamy
• Male-Male Competition and Female Choice
– Multiple criteria, honest signals, good genes
– Arbitrary criteria, runaway selection, exaggerated characters, linkage of genes for female preference with genes for male traits
• Or culture, nestlings imprint on father’s characters
– Alters (bowers)

•Male parental care is rare in animals generally, but common in birds
•What about dinosaurs that have been found with nests?
•clutch volumes much greater than in female-only caring crocs
•clutch volumes more closely matched to birds in which males care for young, suggesting primitive character was polygamy, specifically polyandry
Other dinos
Log (Body mass) archosaurs
(Varricchio et al. 2009)

• Male care in dinos to bi-parental care in modern birds
– Increasing egg size allowed precotial young (which could fly quickly)
– Males could invest in care because female investment in egg itself was already very high
• Male egg guarding then incubation (less needed in tropics, mound nesters as an example today)
– Female birds can only lay 1 egg at a time (1 ovary, ovulation inhibited by presence of an egg in oviduct)
• Better to spread them among several baskets initially (polyandry)
– With parental care, egg size could decrease and more altricial young could be born and cared for
• Females are better off producing more but smaller eggs if they are cared for
• Females could benefit by reducing egg loss to predators or male abandonment by also contributing to care
• Favors evolution of biparental care, then perhaps specialization in distinct male female roles.
(Wesolowsk 1994)

• Polyandry
– Jacana
• Polygyny
– Typically males compete indirectly for females by defending important resources (like foraging grounds in blackbirds) or by attracting females to display grounds (like grouse leks)
– Some birds defend female harems
• Montezuma oropendola
• Males defend colonies of females, alpha male rules (like elephant seal) and gets most of copulations (and pass on most genes)
• Females do all the nestling care
– May occur in other blackbirds
• Cowbirds, grackles where males do not invest in parental care
• Clue to occurrence is sexual dimporphism and grouping behavior of females
(Webster 1994)

• Polygynandry
– Smith’s Longspur
• Females pair and copulate with more than one male for a single clutch of eggs
• Males pair and copulate with two or more females
• Intense sperm competition due to promiscuous females
• Several males routinely feed a single brood
• Not territorial
• All males in a neighborhood sing SAME song
– Allows males to easily recognize intruders and females to mate only with local males who will help her raise brood
Briskie 1999

• Social versus Genetic
• Common Crossbill (Kleven et al. 2008)
– Extrapair paternity seems to be common in socially monogamous passerines, but the genetic mating system of most species is currently unknown.
– no evidence of extrapair paternity among 96 offspring in 34 examined broods.
– Common Crossbills thus seem to represent an exception to the rule of extrapair mating among socially monogamous passerine bird species.
– A potentially important selective pressure preventing promiscuity
– in Common Crossbills is the harsh environmental conditions experienced during breeding at wintertime, which may increase the importance of paternal care and limit the time available for seeking extrapair copulations.
(Moller and Birkhead 1993)

• Migration may limit resources (energy and time) available for investment in parental care and territory defense
• Sexual selection for parental care may reduce time and energy available for migration
– Breeding systems may determine or respond to migration behavior
Shorebirds: Garcia-Pena et al. 2009)

In comparison of shorebirds, it appears that migration drives parental care shift, not vice versa (Garcia-Pena et al. 2009)

More male:male competition leads to increased bias toward male mortality
Female-female competition does not
Parental care also is costly
Liker and Szekely 2005

• Polygyny can be costly
• In sage-grouse modelling study
Ne was only 19% of N because of variation in reproductive success between years and the skew in breeding sex ratio
• Resulted in small effective population (42) which may suffer inbreeding effects (low hatchability was observed
• Need to manage for larger than one might expect population sizes
(Stiver et al. 2008)

• Flexible mating systems may counteract synchronized environmental fluctuations
• When sex ratio becomes skewed, if polygamy can occur, then chance of extinction is reduced
• Lesser Spotted Woodpecker in Germany
– Models suggest that when male skew in sex ratio occurs, then polyandry would reduce probability of extinction
(Rossmanith et al. 2006)

– Fission Fusion

(Brown 1974)

• Alpha and beta male pairs display at leks for females
• Alphas get nearly all copulations
• How are these roles set?
– Social networks early in life are important 4-5 years later
(McDonald 2007)

(McDonald 2007)

• General consideration of tradeoffs to sociality
• Sociality often reduces individual workload, fear, predation, finding unpredictable foods, etc
• Sociality also increases disease, competition, conspicuousness, cuckoldry
• You can predict the optimal group size depending on the various advantages and disadvantages

• (1) Roosts comprised both knowledgeable and naive foragers.
• (2) Departures from roosts were highly synchronized, with most members departing in one direction.
• (3) Direction of departure often changed from day to day.
• (4) Birds made naive of food sources (by being withheld from the wild and then allowed to join roosts) followed roost-mates to new feeding sites, whereas control birds held and released outside of roosts rarely found the local food bonanzas.
• (5) Birds made knowledgeable of food sources (by being released at new carcasses) joined roosts and led roost-mates to the food on three of 20 occasions.
• (6) The same individuals switched leader and follower roles depending upon their knowledge of feeding opportunities.
(Marzluff et al. 1996)

Not Kin Selection
Parker et al. 1994

• Increase foraging flock to optimal
• Depends on if you are subordinate or dominant
Marzluff et al. 1996

Myth
Reality
(at least in Texas
Watts and Stokes 1971)

– Young males form sib groups that remain together for life, coalesce during winter but compete for mates on lek in spring
– Females go to lek and males travel by, displaying as sib groups

(Buchholtz 1997)
Snood Length Matters

If a turkey has a choice, it makes sure its snood is the largest in the group

(Buchholtz 1995)
Snood Length Matters

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77:1587-1594.
•
Brown, J. L. 1964. The evolution of diversity in avian territorial systems The Wilson Bulletin 76:160-169.
• Brown, J. L. 1974. Alternate routes to sociality in jays: with a theory for the evolution of altruism and communal breeding.
American Zoologist 14:63-80.
• Garcia-Pena, G. E., Thomas, G. H., Reynolds, J. D., and T. Szekely. 2009. Breeding systems, climate, and the evolution of migration in shorebirds. Behavioral Ecology 20:1026-1033.
• Kleven, O., Bjerke, B-A., and J. T Lifjekl. 2008. Genetic monogamy in the Common Crossbill (Loxia curvirostra). J. Ornithology
149:651-654.
•
Liker, A., and T. Szekely. 2005. Mortality costs of sexual selection and parental care in natural populations of birds. Evolution
59:890-897.
•
Marzluff, J. M. and B. Heinrich. 1991. Foraging of vagrant common ravens in the presence and absence of territorial adults: an experimental analysis of social foraging. Animal Behavior 42:755-770.
•
Marzluff, J. M., Heinrich, B., and C. S. Marzluff. 1996. Communal roosts of common ravens are mobile information centers.
Animal Behaviour. 51:89-103.
• McDonald, D. B. 2007. Predicting fate from early connectivity in a social network. Proc. Natl. Acad. Sci 104:10910-10914.
• Moller, A. P. and T. R. Birkhead. 1993. Cuckoldry and sociality: A comparative study of birds. The American Naturalist 142:118-
140.
• Parker, P. G., Waite, T.A., Heinrich, B. and J. M. Marzluff. 1994. Do common ravens share food bonanzas with kin? DNA fingerprinting evidence. Animal Behaviour.48:1085-1093.
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Rossmanith, E., Grimm, V., Blaum, N., and F. Jeltsch. 2006. Behavioural flexibility in the mating system buffers population extinction: lessons from the lesser spotted woodpecker Picoides minor. J. Animal Ecology 75:540-548.
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Stiver, J. R., Apa, A. D., Remington, T. E., and R. M. Gibson. 2008. Polygyny and female breeding failure reduce effective population size in the lekking Gunnison sage-grouse. Biological Conservation 141:472-481.
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Varricchio, D. J., Moore, J. R., Erickson, G. M., Norell, M. A>, Jackson, F. D., and J. J. Borkowski. 2009. Avian paternal care had dinosaur origin. Science 322:1826-1828 (and erratum 7 Aug. 2009).
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Webster, M. S. 1994. Female-defence polygyny in a Neotropical bird, the Montezuma oropendola. Anim. Behav. 48:779-794.
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