1. Chapter 12 Mates/Chapter 13 Breeding Systems
March 27th, outside for lab, no lecture
Test 2 April 1st and last day for W
April 3rd, no class or lab – Good Friday break
Chapter 12 Mates/Chapter 13 Breeding Systems

2. Mates and Breeding Systems
Summer Tanager, Piranga rubra
Scarlet Tanager (Piranga olivacea)
Getting genes into the next generation and the differences in what the sexes look to do

3. Mates and Breeding Systems
Note the differences in reproductive output; starting with a primary spermatocyte males will have 4 functioning gametes, starting with a primary oocyte, females will only have 1 functioning gamete

4. Mates and Breeding Systems
Although an insect example, this holds for males and females of all species. For females more mates does not mean more offspring, this, however, is a truism for males – basis of Sexual Selection

5. Mates and Breeding Systems
Precocial development
Altricial development

6. Mates and Breeding Systems
Put gametes, reproductive potential, offspring development, food resources, nesting resources, etc. together
Sexual selection
Second mechanism that Charles Darwin suggested for evolution of species
Two pathways, mate choice and intrasexual competition
The Indian Peafowl (Pavo cristatus) was the ultimate symbol of sexual selection in Darwin’s mind

7. Mates and Breeding Systems
Monogamy – genetic and social
An exclusive pair work together to raise joint young
May be genetically exclusive
Typically, pair are behaviorally exclusive but not genetically
Majority of bird species (~90%) show monogamy
Necessity of both pair members for raising young (typically altricial) and/or defending resources
Pairing may last one breeding season, could last for multiple seasons or for life
Divorce in long-term pairs typically due to reduced reproductive success
Many pairs pursue extra-pair copulations (EPCs) and a large majority of nests contain extra-pair young (EPYs)

8. Mates and Breeding Systems
Multiple strategies have been suggested for why females pursue extra-pair copulations, since more mates do not equal more offspring
The Saltmarsh Sparrow (Ammodramus caudacutus), possibly the worlds most promiscuous socially monogamous bird

9. Mates and Breeding Systems
Polygyny
One male mates with multiple females at one time
Females may be on a territory he controls and the females use
Males may be on a breeding-specific territory – a lek
Typically male does not assist with parental care
Young frequently precocial and two parents are not necessary for raising young
Food resources used by the species are abundant enough that females can care for young by themselves
Females will, again, pursue multiple matings (EPCs) for many of the same proposed reasons as socially monogamous species
Males of many typically monogamous species will try to be polygynous if they can get away with it!

10. Mates and Breeding Systems
In Red-winged Blackbirds (Agelaius phoeniceus) one male can mate with several females who build nests on a territory he controls. Better territories bring in more females.

11. Mates and Breeding Systems
Leks are an interesting area within polygyny
Males defend display area only
Success of some males is huge
Females get genes only
Three popular models
The ‘hot spot’ hypothesis
The ‘hot shot’ hypothesis
Female preference hypothesis
The Andean Cock-of-the-rock (Rupicola peruvianus) is one of many fascinating lekking species, look a few up on YouTube, particularly the manakins and birds of paradise

12. Mates and Breeding Systems
Polyandry
One female mates with multiple males
Many species females behaviorally more like males
Sex-role reversed species
Female in some species lay a clutch of eggs for each male
Linked in some cases to fixed clutch sizes and a mis-match with currently available food supplies
Polygynandry
Best described as a mating free-for-all
Males may mate with multiple females who in turn mate with multiple males

13. Mates and Breeding Systems
Northern Jacana (Jacana spinosa)
Spotted Sandpiper (Actitis macularia)
Two classically polyandrous species, occasional polyandry seen in other species, but it’s rare

14. Mates and Breeding Systems
In sex role reversed species males and females have typical levels of steroid hormones (although they may change for parental care) however females of some species have more receptors for hormones in the brain.

15. Mates and Breeding Systems
Dunnocks (Prunella modularis) a species showing polygynandry and complex behaviors linked to reproductive access

16. Mates and Breeding Systems
Regardless of breeding system or strategy pursued individuals must be able to choose a good mate
Males – quantity is typically preferred (unless he just cannot get away with it)
EPFs allow one to ‘have their cake and eat it too’
But, you don’t want your social helper to be a complete mess
Females – quality is key, she’s limited by the number of eggs she can produce so each one must be tip-top
Gotta have a mate who is the best of who is available to you
However, EPFs can allow for variation in fathers
How to choose?
Ornamentation, the focus of sexual selection

17. Mates and Breeding Systems
Sexual selection – Darwin’s second mechanism
Intrasexual competition
Members of one sex (usually males) compete for access to other sex
Mate choice
Members of one sex (usually females) choose mates
Ornaments used to convey information concerning competitiveness and quality

18. Mates and Breeding Systems
Ornaments can be difficult to conceptualize
Behaviors, songs, plumage colors, skin colors, feather modifications
Not going to help you survive, or forage, or avoid a predator, or keep you warm
Will help you acquire resources needed for reproduction
Will make you a sexier individual
Ornaments will be discussed as being under two general categories
Indicators of condition/quality (‘Handicap’ hypothesis here too)
Run-away selection (aka, Fisherian selection)
Females ‘like’ something and it evolves out of control

19. Mates and Breeding Systems
Ornaments as indicators of behavior, condition, or quality
Some can work in both mate choice and competition
Indicator handicaps – Zahavi
Parasite mediated indicators – Hamilton and Zuk
Good parent hypothesis – Hoelzer
“Good genes” or heterozygosity
Indicators of condition and individual quality
Greatest percentage of work has been done here
Ornaments co-vary with a large number of qualities including; body fat, body condition, immune measures, diet, parasitism rates, body size, feather growth rate during molt, hematocrit, etc.
Often see more than one of the above hypotheses put together
E.g., A highly ornamented bird is in good condition and a good parent

20. Mates and Breeding Systems
Classic work from Geoff Hill’s lab at Auburn University has shown that redder male House Finches (Carpodacus mexicanus) have fewer parasites, have better immune systems, eat better during molt, are more attentive to incubating females, and feed young more.

21. Mates and Breeding Systems
My own work with Northern Cardinals (Cardinalis cardinalis) has shown that more ornamented females are larger, in better body condition, are more aggressive defenders of their nests, breed earlier, and feed their offspring at greater rates

22. Mates and Breeding Systems
Work by Marlene Zuk on Red Junglefowl (Gallus gallus) has shown that males with larger and redder combs have fewer blood parasites (note, this is a polygynous species), females like this
Females with larger combs are behaviorally more aggressive in this species and become dominant in flocks, males like this

23. Mates and Breeding Systems
Male Great Tits (Parus major) with wider black breast stripes have fewer ectoparasites and are dominant in flocks
More ornamented female Barn Owls (Tyto alba) have better genetic-based resistance to parasites and diseases (cross fostering studies by Alex Roulin)

24. Mates and Breeding Systems
Collared Flycatcher (Ficedula albicollis)
Ornaments show flexibility and changes in condition can be reflected honestly in changes in ornament expression

25. Mates and Breeding Systems
Ornaments may indicate higher quality, but are they assessed and preferred?
Overwhelming answer is yes!
Studies where females are allowed to show the researcher they choose the more ornamented male
Mate choice aviaries where males of two appearances are demonstrated
Manipulation studies (either directly or through diet if possible) where ornaments are changed
Assessment of new pairings of birds

26. Mates and Breeding Systems
In the Long-tailed Widowbird (Euplectes progne), a polygynous bird, females prefer males with longer tails. This can be seen in natural variation and following manipulation.
Here a male is displaying his tail

27. Mates and Breeding Systems
Sticky-wicket in the ornaments – most birds have more than one and more than one type
Song, melanin coloration, ultraviolet reflectance, a physical display
How do these function?
Multiple message – each conveys information on quality
Different types of ornaments can be strongly linked to specific types of quality
Redundant signal – each says the same thing, it’s just repeated
Unreliable signal – only one is an actual indicator, the others are no longer accurate indicators

28. Mates and Breeding Systems
Mostly unreliable ornaments
Multiple messages conveyed here

29. Mates and Breeding Systems
Many questions remain about ornaments
How did they evolve?
Run-away suggested initially
How do ornament expressions get linked with quality?
Common denominator like dietary components key
How do ornament expressions get linked with behavior?
More complex and may be due to linked genes
Similarities in ornaments/displays among closely related species and between males and females of a single species
Shared ancestors and shared genes

30. Mates and Breeding Systems
Some unique breeding systems need to also be considered
Brood parasitism
Many species participate in ‘egg dumping’ – opportunistic parasitism of your own species
Intraspecific brood parasitism, may be more wide-spread than previously thought
Some species are obligate brood parasites
These species do not raise their own young
Many unique adaptations of physiology, eggs, and behavior have occurred in the brood parasites
Typically the parasite is detrimental to the host reproductive success
Parasites often kill the host’s actual young

31. Mates and Breeding Systems
Common Cuckoo (Cuculus canorus)
Brown-headed Cowbird (Molothrus ater)
Many interesting adaptations occur in both these species to more accurately manipulate their hosts

32. Mates and Breeding Systems
Hosts are not without defenses
Unusual nestling markings to identify parasites
Unique egg markings to identify parasites
Rejection of non-typical eggs
Some species can just deal with the intrusion
Some species can out-compete the parasite
Cut-throat Finch Amadina fasciata

33. Mates and Breeding Systems
North American Cuckoos show flexibility in their nest parasitism behavior

34. Mates and Breeding Systems
Cooperative breeders – many working together
Young individuals stay home to assist their parents in raising siblings - More common cooperative breeding
Often linked to territory/resource availability
Indirect fitness – full siblings share your genes, it’s better than nothing
These individuals are usually fully capable of breeding

35. Mates and Breeding Systems
If resources, territories, or conditions are not readily available or conducive for new breeders it may be the ‘best of a bad situation’ for young birds to stay with parents.

36. Mates and Breeding Systems
Florida Scrub-Jays (Aphelocoma coerulescens) are a classic example of cooperative breeders.
Helpers are capable of breeding, but have no territory to go to, so they stay and assist parents in raising more offspring.
Steve Schoech with a jay – his favorite photo

37. Mates and Breeding Systems
Helpers help in various ways and can greatly impact success of breeding pairs, this leads to conflicts between helpers and breeders. Helpers are frequently looking for some sort of benefit from breeders.