ADVANCED LEC 16ORNITHOLOGY

University of Rio Grande

Donald P. Althoff, Ph.D.

ReproductionPart I

Reference Chapters 12 - 17

Reproductive Behavior

• _________________ = gamete shedding• _________________ of all kinds of mating systems• __________ of mating systems

• COMPLEX: a) _________________—involves courtship

behavior b) _________________—all species of birds do

this c) _________________

* pre & post highly variable among birds

Mating Systems• Considerable variety in pair bonds for birds—ranging

from _______ sexual union to __________ mutual efforts:

1) monogamy – “mono” + “marriage”2) polygamy – “many” + “marriage”3) polygyny – “many” + “woman”4) polyandry – “many” + “man”5) polgynandry – “many” + “woman” + “man”6) promiscuity – “pro” + “mix”

Greek for…

Mating Systems Largely Driven by Coloration and Vocalizations

• Typically, males ____________ than females• Combination of coloration and vocalizations result in

breeding displays…much variety across the class Aves

• “Experience” matters…as older males tend to be have better songs than young males

• Color “_________________” ….and size influences rate of breeding opportunities

• Note: songs – breeding/mating vocalizations vs.calls - feeding, begging, alarm, flock communication

Monogamy –____________________

• “the” predominant avian mating system• ______ of bird species (but % probably continuing to

______ because of DNA evidence on paternal “contributions” to clutches…suggesting promiscuity)

• Prolonged and essentially exclusive bond with a single member of the opposite sex for purposes of raising young.

• Appears common among passerines, raptors (hawks and owls)

• Common among geese and swans…all Procellariformes (remember: albatrosses) and Sphenisciformes…all ____________________________________________

F + M

Monogamy – __________________

• Male remains around until fledging• Common among

a) gullsb) grebes

c) many passerines (woodpeckers, bluebirds—which have multiple clutches/broods

d) mourning doves—which have multiple clutches

F + M

Monogamy – Pair-Bond until _________________

• Together until all eggs laid…before ‘split’ before incubation starts

• Many ducks (Anatidae)• Some phalaropes (where clutch is laid, then female

leaves and male incubates)

F + M

David Lack – _______(one of the pre-eminent ornithologists)

“Well-over nine-tenths (93%) of all passerine subfamilies are ___________ ____________….Polyandry (multiple male mates) is _____________.”

Today, through DNA analysis…we know this above statement to be wholly false.This is known as “DNA fingerprinting”

Gill Fig 12-21 p361

“________” the pair bondpaternity (i.e., extra-paternity)

Thus, over ______ of pair-bonded species

have “outside” thepair bond contributions

Thus, only ~_____ truly monogamous

Pairing - Miscellaneous

• Wood thrushes and ptarmigan: no obvious sexual dimorphism (although maybe UV-perceptible???)– mates take longer to work out acceptance

• Geese and swans: pair in 2nd year of life with a very long “engagement period”

• Swans: some waiting to have engagement and mate for 3 to 5 years

F + M

Variation within a Family: MEGAPODIDAE

• Willow ptarmigan: monogamous, well-developed/ established territory

• Ring-necked pheasant: polygamous, ill-defined territory, not necessarily where females will nest

• Black grouse: small, well-defined territories with alpha/master cock. No help of males in rearing young

Polygamy

• Any mating system involving pair bonds with ________ mates of the opposite sex

• These are all “subsets” of the polygamy category:

F + M.…MM + F...F

Polygyny Polyandry Polygyandry

Polygyny• ______ of bird species (but % probably continuing to

________ because of DNA evidence on paternal “contributions” to clutches that we originally thought had monogamous status)

• Male pairs with 2 or more females (bigamy if M with 2 F).

• Sustained association with the females (pre- and post-copulation) separates this from promiscuity

• Example: red-winged blackbirds • _______________________ male controls access to

critical resource like nesting habitat and/or food resources. More common where “patchy” distributions of these resources

M + F…F

Polygyny..con’t

• _______________________—males are not defending females nor are they defending a resource. Instead, males compete for females by establishing “dominance” or by demonstrating their quality through displays.

Aggregations of many males in a smallarea are called ______

ex. prairie chickens sage grouse

sharp-tailed grouse

V

Leks…what favored evolution of this approach to breeding? A couple of hypotheses…

• _________—_____ gather at a location where they are most likely to encounter roaming females. Gives male(s) a chance to establish strategic position (usually center of lek) to convey dominance

• _________—________ can go to a group display which facilitates comparisons which male is the “best”/most fit is more easily determined. Assessment can be made more rapidly (in a few minutes, even) than if she had to visit each males with territories scattered across a landscape

AFRICAN LONG-TAILED WIDOWBIRD

Polyandry

• _____ of bird species • Female pairs with 2 or more males • Sustained association with the males (pre- and post-

copulation to varying degrees) • Males tend to the clutch, stay with hatchlings• Females tend to be more brightly colored than males• Examples: phalaropes, spotted sandpipers• ________________________ female controls access to

critical resource like nesting habitat and/or food resources. More common where “patchy” distributions of these resources. Clutch sizes usually small

F + M…M

____________________

2♂♀

Polyandry…con’t

• ______________________ – female lays full clutches of eggs for successive mates…thus, incubation of eggs/nests are not essentially overlapping.

Advantage: __________________________ vs.

• _____________________ – female lays full clutches of eggs for two or more mates during the same time period…thus, incubation of eggs/nests are essentially overlapping. Advantage: ___________________________

Polygynandry

• _____ of bird species• Female pairs with several males, each of which also

pairs with several different females

• Common among the tinamous, the flightless ratites (ostrich, rheas, emu), and some songbirds (Smith’s longspur and hedge accentors)

• Among _______ and tinamous, males incubate mixed clutches of eggs from several different females, which deposit eggs successively with different males

F1 + M1, F1 + M3, F2 + M1 etc.

Promiscuity

• ______ of bird species

• Indiscriminant sexual relationships—usually of ______ duration

• Examples: male hummingbirds and male manakins (…and technically, one could classify grouse species—lek or non-lek like the ruffed grouse found locally as promiscuous)

Promiscuity…con’t

• Advantage for ______:1) chance to “spread” genes around with

multiple females (not all “genes” in one basket, so-to-speak )

2) can sire more offspring in _________breeding season

3) __________________________…so if predator

takes out one nest, he still may end upsiring offspring that breeding season

Promiscuity…con’t

• Apparent advantages for ________:

1) Some males are more fertile than others, so reduce risk of incubating infertile eggs

2) “________” hypothesis: female increases fitness of her male offspring by mating with a male who has especially attractive _______________ characteristics

Copulation

• Copulation—in and of itself—is usually not important in pair formation…but everything leading up to it is!

• Some duck species: semen may be good for 14 days in female’s reproductive tract, which is good for fertilizing the entire clutch

• Waterfowl: males usually have specialized copulatory structure…an “extension” of the cloaca) (see next slide)

• Some species (coots and gallinules): the female mounts the male

GA

LL

IFO

RM

ES

AN

SE

RIF

OR

ME

S

Chicken Quail

Duck

Goose

Lack extension Penis-like structure

Egg laying & Nesting/Parental Care

• Nest preparation variable, ranging from…a) _______ (just “lay” eggs) (ex. Nighthawks,

fairy tern)b) _______ (ex. gulls)

c) _______________ (ex. piping plovers, killdeer) d) _______ a nest (most common) e) _______ a nest (ex. weaverbirds, orioles) f) _______(many years, in some cases… ex. eagles, hawks)

• Value of nest with respect to incubation of eggs:a) _________ provided for development

b) _________ to many predators

Oviparity• Considering the diversity of birds…including a wide

variety of mating strategies….all are limited to laying eggs

• All lay a single egg laid at a time (usually 24-36 hours between eggs). ______________________________ _________….multiple eggs are retained in the oviducts of the female for extended (>24-36 hr) periods of time. The strategy of viviparity suggest that for this group of vertebrates, the benefit of egg retention outweighs its cost (makes sense in “cold climates”—eggs can start to develop sooner). Vice versa with respect to birds…laying one egg per day, then incubating them all must outweigh the cost.

Fig. 17-29 p473, PJH

1

2 2

2

3

4

• Site of fertilization• Albumen and shell

membranes (not shell) are secreted

• Egg enclosed in calcareous shell

• Deposited

12

3

4

ovary infundibulum

shell gland

cloaca

Different patterns of Laying Eggs• Some species are ________________ layers:

a) a fixed number of eggs are laidb) usually those species that

have 1, 2, 3, 4, or 5 eggs for an average clutch size.

c) remove and egg and they probably won’t lay a “replacement” egg d) example: piping plover

• Some species are ________________ layers:a) not usually a “fixed” number of

eggs b) usually those species that have 10 or more eggs for a

clutch c) remove an egg or eggs and they just keep laying (example: chicken)

Different patterns of Incubating Eggs• Some species start to incubate eggs after 1-2 are laid

even if clutch ends up being 3-5 or more eggsex. Most raptors (hawks and owls)….results

in _________________ hatching of young

advantage? ______________________

• Some species do not start incubation until all eggs in the clutch are laid. Common among species with small clutches (i.e., 2-5) and large clutches

Results in __________________ hatching of young

advantage? _______________________

The Egg• Inorganic part of the eggshell contains about 98%

crystalline calcite (CaCO3)…and the ________ obtains about _____ of its calcium from the egg shell.

• Two shell membranes are secreted to enclose the yolk and albumen:

a) “outer” shell membraneb) “inner” shell membrane…..

…as these membranes are laid down, H2O and carbohydrates are added to the albumen via active transport of Na & osmotic flow of H20.

• Mammillary bodies are sites of calcite crystal forming

Fig. 17-31 p474, PJH

Mammilary core

Outer shellmembrane

inner shellmembrane

chorioallantoicmembrane

embryo

The Egg…con’t• Changes in fluid concentrations surrounding the egg

change as the shell is put down, with increased concentrations of Mg and P…and a pattern in the change of crystallization in the surfaced layers of the shell

• In “end” product, pores are present that allow O2 and CO2 to diffuse in and out, respectively. Pores represent about 0.02% of the surface of the eggshell

• ________________________ serves for gas exchange until 1-2 days before hatching. Air cell at the blunt end of the egg is punctured by about to hatch chick and ventilation of lungs takes over gas exchange

• Egg tooth helps chick “saw” its way out!

Fig. 17-31 p474, PJH

chorioallantoic

membrane

Pores—not all are ‘straight’

Next time…

More eggs and nests