Download Exam II Answer Key

Ornithology Spring 2014. Exam II.
Name:
(1) In the Life of Birds video we watched, Village Weavers have an adaptation against brood
parasitism by having a polymorphism for egg color; in other words, each female lays eggs of a
single color, but within a population or colony different females lay eggs with different colors.
How does this protect them against brood parasitism by Diederick’s cuckoo? (If you didn’t see
the video the brood parasitism pdf I asked you to read gives a similar example).
Generally good answers. The key here is that b/c weavers are individually variable (for
egg/pattern) and cuckoos are not, cuckoos don’t know if their egg color matches that of any
individual weaver they parasitize. So the weaver tosses out the odd (cuckoo) egg. And since
each individual weaver is distinct, cuckoos cannot have an effective egg mimicry strategy. They
will be lucky sometimes with a random match, but not often.
(2) Plumage color patterns may serve to communicate rank as in Badges of Status. What is a
badge of status (i.e., what does it communicate?) and what common Lubbock bird employs this
strategy?
House Sparrow. Bade of Status communicates dominance and/or level of aggression, which
often reflects age.
(3) Females preferring males with head crests when they don’t actually grow a crest is an
example what phenomenon?
Sensory Bias. If you wrote Arbitrary mate choice I took one point off. It's a perhaps subtle
distinction in this case, but these experiments are a direct test of the former and not the latter.
What species has this experiment been done on?
Zebra finches
(4) Name a species or a specific group that widely applies the following to account for coloration
patterns (that may change over time):
Melanins:
lots of answers
Carotenoids:
lots of answers
Interference patterns of light: grackles, hummingbirds
Feather wear:
E. Starling, meadowlark, snow buntings
(5) What is the likely cost (in 5 words or less) of the following characters/displays (each answer
MUST be unique): Answers were generally good. However, one must read the question and
understand what the cost is. If you say long tails decrease escape speed from a predator and
orange coloration makes you more visible to a predator you have invoke the SAME cost – higher
predation risk. To indicate unique costs you can indicate long tails are energetically costly to
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produce or maintain, and compromise flight efficiency and hence drain energy (these are ALL
ENERGY COSTS). Or change your answer to (2): carotenoids impair the immune system.
(1) Long-tailed widowbirds:
(2) Bright orange or red color of Cock-of-the-Rock:
(3) Rushing display (‘running’ over the water) of Western Grebes:
(6) In contrast, asymmetry in otherwise symmetric ornamental traits does not necessarily have a
cost, but what DOES asymmetry reveal (be specific)?
Developmental stress; I did except some other answers or give partial credit the your answer was
worded differently.
Give an example of a bird with a symmetrical ornamental trait.
Lots of examples.
(7) Why do we use the qualifier ‘socially’ when referring to monogamy among birds?
I was really looking for EPCs. Using the acronym was fine, since that’s how ornithologists say
it. This was one if the questions (only 2 pts) I graded pretty much black-or-white.
(8) Match the following
Dunnock
B
Superb fairy wren
C
Florida scrub jay
A
Sage Grouse
Greater honeyguide I
Acorn woodpecker D
White-winged chough
Superb Lyrebird
F
Brown-headed Cowbird
A.
B.
C.
D.
E.
F.
G.
H.
I.
not used
E
Cooperative breeder with helpers acting as extra sentinels
Has a highly variable mating system (monogamy, polyandry, polygamy, promiscuous)
Has the highest known extra-pair copulation rates
Communal breeder where alpha male partially gives up reproductive rights to helpers
Brood parasite; has contributed to the near extinction of Kirtland’s warbler
Sexual displays includes mimicry (even the sound of chainsaws)
Lekking species
Conduct ‘kidnapping’ of juveniles to assist in raising their own young
As nestling they a stabbing ’tooth’ at the end of the beak to kill other nestlings
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(9) Draw a simple graphical model (i.e., as in class) and USE IT TO SHOW how signals that are
costly to produce can result in honest communication about, e.g., a male’s quality. For credit,
you MUST correctly label your axes and any other relevant components.
Come and see me if you have questions. There is an example in the mate choice PP notes of
what the correct figure looks like. Points taken off for incorrectly labeled axes, or a poorly
drawn graph. I did give bonus points (up to +2) if you offered a written sentence or two
explaining the graph.
(10) You are studying a bird species that is a facultative cooperative breeder and you pose the
habitat/territory saturation hypothesis as an explanation. Describe how you could experimentally
test the habitat saturation hypothesis, and what result would lead you to accept the hypothesis
and what result would lead you to reject it?
Students did very well in general. Exceptions occurred when answers were in relation to NOT
about Coop Breeding (mate choice for example). I also asked for evidence to accept AND to
reject the hypothesis. So you must have both for full credit. The most direct answer was
transferring a coop breeder to an island (or uninhabited area) and following the breeding patterns
– see PP notes on the Seychelles warblers under Coop Breeding lecture.
(11) Answer the following in terms of our cost-benefit approach to understanding the diversity
of mating systems in birds. Social monogamy (the most abundant mating system in birds) is
driven by what – there are two factors: give them as algebraic expressions AND put it into
words.
Second, defend those expressions by referencing empirical support in birds (e.g., case studies or
observations from class). Be as specific as you can and use material from any lecture topic that
is relevant. Hint (incomplete): why is it that males matter?
Two factors: P2 >> P1: You do need to define the terms or put into words: the probability of
raising offspring is much higher with 2 parents versus 1. Second, pm (opportunity of the male to
remate if he abandons) is very low. Together you can also write (but not required) P2 >
P1(1+pM). A verbal description without the mathematical formulism will not be full credit;
however; I put emphasis on the verbal.
Part tow: Why do males matter? We spoke at some length on this so I expect a more than
superficial answer. For instance, limiting your answer to saying having two parents increase
success results in a bare minimum of points. I do expect you should know at least one case study
and a couple examples of what males do. A good answer also fits the observation to the
question.
For ex: Male woodpeckers build nest cavities so females can invest resources into parental care.
In hornbills, female are completely dependent on males to provide them with food when the
former are enclosed in cavities with young. W/o the male reprod success will be zero. Last,
numerous studies have shown that removing the male at almost any period in the reproductive
cycle leads to a reduction in young (e.g., 7 of 8 studies removing male kestrels resulting in nest
abandonment in females).
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(12) European cuckoos and Brown-headed cowbirds are both brood parasites. However,
cuckoos are not responsible for the near-extinction of any host species, whereas brown-headed
cowbirds are. Why the difference? There are several reasons, give as many as you can, but
specifically how is being a host generalist/specialist relevant? Be complete.
I gave emphasis on the Spec/Genral distinction – the answer is framed that way. Most of you
knew this and did well. But you needed to include something to the effect of:
Cuckoos specialize on individual host species. Therefore, if parasitism is so high the host spp
declines, with a rare host, cuckoos will also subsequently decline (negative feedback on the
population) and host population can build back up. Cowbirds are generalists (dozens and dozens
of host spp), so they can drive a one or more hosts to extinction without negative feedback, since
there are many alternative host species still available to parasitize.
(13) Name a species threatened with extinction in part due to cowbirds.
Kirtland’s warbler was the most common answer
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