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

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

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

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

Mates and Breeding Systems Precocial development Altricial development

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

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)

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

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!

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.

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

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

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

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.

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

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

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

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

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

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.

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

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

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)

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

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

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

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

Mates and Breeding Systems Mostly unreliable ornaments Multiple messages conveyed here

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

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

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

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

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

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

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.

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

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.