Ornithology Exam 2

Arctic Tern

Bird species that migrates/travels most of its life

Bar-tailed Godwit

Bird species that can travel 6800 miles in week with zero stops

How migration is studied (4)

Citizen Science, Radar, Tracking, Stable Isotopes

Citizen Science for Migration

**George Lowery**, observed using silhouettes across the moon

Ebird

Radar

Doplar observation of flocking groups

Tracking

Cutting-edge observation. Able to be used on individuals, not just groups

Allows studies on long migratory patterns

Easier to do with larger birds and even some smaller Passeriformes, but does have size limitations

Stable Isotopes

Use ratios in feathers to infer their locations because of natural variation, has largely gone out of use

Why birds migrate ()

1. Allows species to exploit resource-rich environments during abundance, and depart during harsh periods
2. Means of allowing species to maintain food availability and favorable conditions

Change in percentage of migratory species along latitude lines

Closer to the equator, fewer migratory species

Main driver of timed migration

Changes in photoperiod

Other impacts to migration timing

Proximally, immediate weather conditions also impact

Goal of timed migration

Ensures arrival during peak resource booms

Cliff Swallows

Incredible species capable of consistently migrating within just a few days difference each year

Phenotypical flexibility

Special category of reversible changes in individual phenotypes comprising flexible responses to changing tasks

How do birds prepare for migration

Changes due to phenotypical flexibility, caused by hormonal changes

Types of migration preparation (4)

Molting, hyperphagia/fattening, growth/decrease in muscles, digestive organ atrohpy

Molt changes for migration

Flight feather growth occurs prior to the start of migration, body plumage occurs during migration to provide mating signal upon arrival at breeding ground

Hyperphagia and Fatting for migration

Gain 50% of body mass in 1 month, most of which is fat and not muscle

Intestine and liver mass both increase

Why store fat for migration (4)

1. Highest concentration of metabolic energy per unit weight
2. Can be stored without water or protein
3. **Efficient oxidization by most tissues**
4. Strengthens fatty acid-reliant muscle fibers needed for flight

Growth and Decrease in muscles for migration

Pectoral and heart forms grow significantly prior to migration, leg muscles decrease right before departure

Digestive organ atrophy

Increase during hyperphagia, but prior and during migration decline significantly

May be for weight-saving and/or due to fasting during migration

Stopover Sights

Critical for replenishing for a short period of time during migration

Importance of stopovers (4)

1. Sleep (especially during the daytime)
2. Recovery from oxidative stress (exercise causes cell damage)
3. **Organ regeneration**
4. Recovery of fuel supplies

Swainson’s Thrush

Commonly use stopover sights for SIGNIFICANT increase in daytime sleep compared to when nonmigratory

Stopover consistency

Many species are able to pinpoint year after year the best places to stop to recover during migration

Sandhill Cranes

Species with incredible stopover consistency in Central Nebraska at the Platte River.

Manx Shearwater

Tested and able to return to burrows in Wales after being sent to Boston by MAZZEO

California Sparrows

Moved to Maryland and Louisiana from San Jose, missed the summering location but able to return to San Jose to winter. Were unable to do so from Korea. **All by Medwalt in 1960s and 1970s.**

Methods of Migration Navigation (5)

1. Landmarks
2. Star Compass
3. Sub compass
4. Geomagnetism
5. Odor

Navigation by Landmarks

Achieved by following landmarks like roads, rivers, railways. Naive birds cannot use, so must also have some other method of navigation

Homing Pidgeon

Able to follow roads and railways, but use other cues especially prior to learning the landmarks

When not exposed to sun, and magnetic signal was disrupted, unable to effectively migrate

Navigation by Star Compass

Orienteer by the position of stars in the sky. A learned trait that only works when young birds are exposed to the night sky

Indigo Buntings

Example of Star Compass Navigation. Tested using Planetariums and Emlen Funnels. When exposed to night sky or exactly the same on the planetarium, consistently fly Northeast. When sky mirrored, fly southwest. When stars turned off, are unable to determine a specific direction of travel, suggesting reliance on stars for migration. Young birds will learn to navigate only if see stars during first month, with orient in direction of the sky they were raised under. Conducted by stephen emlen in the 1970s.

Emlen’s Results on Star Compasses and Indigo Buntings

Indigo buntings rely on constellations wtihin 35 degrees of North Star, able to use others if a star is blocked out. Birds with opposite photoperiods orient south, rather than north like spring photoperiod birds.

European Starlings

Species that relies on the sun for spring migration and are able to correctly orient when can see the sun, but otherwise scatter.

Navigation by Geomagnetism

Achieved using two sensory systems:


1. Photopigments (Cryptochromes) in the retina that detect poleward/equatorward directions
2. Magnetite and receptors in trigeminal nerve for magnetic polarity

Reed Warblers

Appear to primarily rely on geomagnetism. When displaced and allowed to fly naturally, able to travel in the correct direction. But when exposed to a simulated shift in magnetism, it caused them to fly completely incorrectly.

Navigation by Odors

Limited in scope and usage. May be used at close proximity to distinguish nests from others. Seabirds especially use to forage and find burrows.

Learned versus Innate Navigating

Young birds get lost more easily and may learn routes from adults. Short-distance use geomagnetism and supplement with visual cues. Long-distance use celestial compass and supplement with visual cues and the sun.

Whooping Cranes

Learn fly routes from parents, leads to narrow corridor of passage. Operation Migration sought to teach some birds to use a different fly route and destinations, leading to greater conservation potential for the species.

Barn Swallows

Have undergone a recent migratory shift. Largely breed in the northern hemisphere and winter in the southern, but in 1980s a non-migratory breed population rose in Argentina.

House Finchs

Have undergone a recent migratory shift. Were introduced to Long Island from Southern California, and while 80% in California are nonmigratory, more and more individuals in the NY population have begun migrating.

Annual Cycles

Important parts of a birds year that are recurrent. Namely, migration, breeding, and molting.

Ultimate Reasons for Annual Cycle Timing (Why do these things happen, external selective pressures) (3)

1. Food
2. **Nest sites/territory quality**
3. **Predation**

Impact of food on annual cycles

Attempt to time migration and breeding so that the peaks in food biomass are at their greatest with hatchlings are demanding the most food.

Impact of nest sites on annual cycles

High degree of competition for nest sites, leading to earlier migration to arrive before competition.

Proximate reasons for annual cycles (how are annual cycles triggered, internal) (2)

1. Endogenous clocks
2. Modifying factors in the environment

Endogenous clocks and annual cycles

Hormonal changes/cues that are largely driven by changes in the photoperiod.

Modifying factors and annual cycles

Changes in temperature, rainfall, or the appearance of food may impact the specific time of migration and mating on a finer level than the ultimate reasons do.

Dark-eyed Juncos

Species with strong recent change in the annual cycle. Population that are typically montane, now found at UC San Diego with changes in clutch size (more), aggression/stress (lower), and male parental care (more)

Life History Strategy

The anatomical, physiological, and behavioral adaptations that control how individuals invest in reproduction and self-maintenance in response to their environmental conditions.

Wandering Albatross

Example of slow life history, resulting in later maturity, smaller clutch sizes, fewer broods, and low mortality

Song Sparrow

Example of fast life history, resulting in early maturity, large clutches, more broods, and high mortality

Fast Life History Elements

Age of Sexual Maturity: 1 year

Clutch Size: multiple eggs

Number of Broods: several per year

Lifespan: several years

Adult Mortality: 50%/year

Slow Life History Elements

Age of Sexual Maturity: 8-10 years

Clutch Size: 1 egg

Number of Broods: 1 every couple of years

Lifespan: decades

Adult Mortality: 5%/year

Lifetime Reproductive Success

Cumulative result of annual reproductive success, impacted by age at breeding and lifespan

Annual Reproductive Success Elements (4)

1. Number of nesting attempts
2. Success of nesting attempts
3. Number of eggs in each attempt
4. Age and experience of the bird

Increases in mid-life for many species as fit but also experienced

Montane Juncos have

1 clutch per year, **shorter breeding seasons**, higher aggression, lower male parental care, higher testosterone, higher cortisol, and a higher stress response.

Urban Juncos have

**4 clutches per year, longer breeding seasons**, lower aggression, higher male parental investment, lower testosterone/cortisol/stress response.

Small clutch sizes are driven by:

Low elevations, tropics, **vulnerable nests**, large bodies, altricial young

Large clutch sizes are driven by:

High elevations, temperate/arctic, **secure nests**, small bodies, and precocial young

Why latitude/elevation impacts clutch sizes

Highly variable seasonality and impact to resources, so may be better to have all young when conditions are favorable, which is a shorter time frame at high elevations/latitudes

Food availability hypothesis

clutch size is adjusted by natural selection to maximize the number of nestlings that parents can feed and successfully raise

Predation Hypothesis

High predation rates could select for smaller clutches because laying large clutches puts mother at risk, larger clutches are nosier and require more visits, and risks fewer young at a time.

Warblers

When predators are removed, the parents deliver food more often, in smaller quantities

Precocial Young Qualities (5)

Plumage: Downy

Eyes: Open/alert

Legs: Strong

Mouth lining: Variable

Nest Site: On ground

Altricial Young Qualities (5)

Plumage: Naked skin

Eyes: Closed

Legs: Weak

Mouth Lining: Obvious

Nest Site: Variable

Northern Cardinal

Clutches of up to 5 eggs, with altricial young

Gambel’s Quail

Clutches of up to 15 eggs, with precocial young

Life History Tradeoffs

Pros and cons that result from variable conditions in life history

Dark-eyed Junco Testosterone Test

Higher testosterone males had:

Pros: **larger territories**, higher singing frequencies, high numbers of matings, higher numbers of offspring, higher annual reproductive success, **more foraging**, more movement

Con: more aggressive interactions, lower offspring quality, lower survival, lower total lifetime reproductive success, increased stress hormones (corticosterone), r**educed immune function, lower antibody production, quicker loss of fat stores, less sleeping**

The control males had the opposite conditions

Social Weaver

Capable of creating complex 100+ pair condo nests

White tern

Nest is essentially an indent into the ground

Order of nest structures from most to least flight proficiency required/safety (5)

1. Complex elevated
2. Cavity
3. Simple Elevated
4. Platform
5. Ground

Ground Nests

Widespread across taxa, usually flightless or minimally flighted, surface or buried

Platform Nests

Water-based, made of vegetation to protect from terrestrial predators

Burrow Nests

Safe from the elements but suseptable to snakes and other predators

Simple Elevated “Cup” Nests

Wide spread, especially Passerines. Delicate structures in trees. Away from ground predators but exposed to elements. Pouch/Oven forms protect from elements

Cavity Nests

More safe that terrestrial nests and enclosed, Usually in trees. Hard to construct resulting in heavy competition

Adherent Nests

Only possible for very strong fliers, made from all sorts of materials. One of the safest forces of nests

Innate element of nest building

Type of nest is fixed, even if raised in captivity away from any learning source

Learned element of nest building

Quality of nests are learned and take time to develop

How do woodpeckers make cavity nests (3)

1. Longer lower mandible that directs force away from brain
2. Elongated hyoid bone absorbs shock
3. Spongy layer of bone on skull front absorbs shock

Drivers of mating system variation (2)

1. Operational Sex Ratio
2. The Environmental Potential for Polygamy

Operational Sex Ratio

The average ratio of fertilizable females to sexually active males at a given time

The Environmental Potential for Polygamy

The degree to which multiple mates, or the resources critical to gaining multiple mates, are economically defendable

Monogamy

When sexes or resources are not limiting and sexes are evenly dispersed.

Social pattern where one female and one male associate during the breeding season

90% of bird species are socially ______

Polygamy

When one sex or resource is limiting or one sex is spatially restricted

Extra-Pair Copulations

Mating outside of the socially-established monogamous bone. Often initiated by females in “morning chorus”, resulting from her leaving the nest.

Why seek out EPCs (4)

1. Males increase fecundity with little cost
2. **Females decrease inbreeding risk and increase heterozygosity**
3. Females seek ideal alleles from other mates that her mate lacks
4. Females may find greater genetic compatibility with other males, producing better offspring

Drivers of EPC Frequency (2)

1. Decreased male paternal care in young
2. **Increased adult mortality**

Risks of EPCs (2)

1. Males leave mate, nestlings, and territory unguarded
2. Males may decrease nest defense and provisioning if they are aware their partner is cheating

Conditions for Monogamy (2)

1. Male participation is essential for raising young
2. Males cannot monopolize resources necessary for supporting extra mates

Resource Defense Polygamy

Individuals defend resources essential to the opposite sex

Purple-throated Carib

Species that practices Resource Defense Polygamy, defend key flowers that are clustered

Harem Defense Polygamy

One sex is gregarious for reasons unrelated to reproduction, self-clumping tendencies facilitate direct monopolization by the opposite sex

Ring-necked Pheasant

Species that practices Harm Defense Polygamy

Male Dominance Polygyny (Lekking)

Males do not directly defend females or resources essential to females, but rather sort out among themselves their relative positions of dominance. Females chose males primarily on the basis of male status. Occurs due to low male parental care.

Golden-collared Manakin and Greater Sage Grouse

Species that practice Male Dominance Polygyny/Lekking via selection for ornaments and displays

Simultaneous Polyandry

One female mates with multiple males at the same time. Evolves when females lay more eggs than one male can service.