Eggs - PowerPoint PPT Presentation

About This Presentation
Title:

Eggs

Description:

Eggs – PowerPoint PPT presentation

Number of Views:178
Avg rating:3.0/5.0
Slides: 58
Provided by: nealmu
Category:
Tags: eggs | rium

less

Transcript and Presenter's Notes

Title: Eggs


1
Eggs
2
Egg - Final Form
3
Egg - Final Form
4
Eggs - Large vs. Small Birds
  • Larger birds produce larger eggs
  • Relative size of egg declines as bird size
    increases
  • E.g., small birds egg may be 15 of weight,
    large birds lt5

5
Egg Shape
  • Shape related to shape of birds pelvis
  • Rounded to elongated

6
Egg Shape
  • Shape related to nesting habitat
  • Pointed eggs roll in circle

7
Egg Color
  • Originally white
  • Natural selection has favored colored eggs
  • Inconspicuous

8
Egg Color
  • White eggs found in
  • cavity nesters,
  • those that cover eggs when they leave,
  • or sit on them immediately after laying first egg

9
Egg Color
  • Many solid colors, lots of spotting
  • Usually species-specific colors, patterns

10
Egg Laying
  • Laid at time so that hatching occurs when food
    for young will be abundant
  • Owls - winter
  • Insect-eaters - spring

11
Egg Laying
  • Most common laying time - morning
  • Common to lay one egg/day until clutch complete

12
Egg Laying
  • One egg/day - most songbirds, many ducks,
    woodpeckers
  • Many larger birds have greater time period
    between eggs

13
Clutch Size
  • Much variation
  • Patterns among birds highly variable
  • Larger birds may have fewer eggs than small
    birds, but not hard and fast rule

14
Clutch Size
  • General latitude pattern within same or closely
    related species
  • More eggs further north
  • Better resources
  • Longer days to find food
  • Fewer predators

15
Replacement Clutches
  • Most birds capable of renesting if initial
    nesting attempt fails (except large birds with
    long incubation periods)
  • Repeat courtship, copulation, and so on

16
Multiple Clutches
  • Many birds raise multiple broods during a single
    season
  • Eastern Bluebird - 2 or 3/season
  • Tree Swallow - only 1/season

17
Determinate Layers
  • Stop laying eggs after fixed number produced
  • If 1 or more destroyed, it cannot be quickly
    replaced

18
Indeterminate Layers
  • Keep laying until they have enough, even if some
    are destroyed
  • Destroyed ones can be replaced quickly

19
Incubation
  • Two basic strategies
  • 1) Start immediately
  • 2) Wait

20
Incubation
  • Strategy 1 Start immediately after first egg is
    laid
  • Loons, owls, hawks eagles, gulls, hummingbirds
  • Long incubation period during bad weather

21
Incubation
  • This strategy produces hatching asynchrony
  • Young hatch in same pattern as laid
  • Large age/size differences among nestlings

22
Incubation
  • Strategy 2 Wait
  • Start incubation after last egg of clutch is laid
  • Ducks, geese, Galliformes, most songbirds
  • Short incubation, better weather

23
Incubation
  • This strategy produces hatching synchrony
  • All eggs hatch on same day
  • All nestlings the same age/size

24
Incubation Brood Patches
  • Contact between body heat, eggs
  • Single, bare skin area develops in most birds
    (songbirds, raptors, pigeons)
  • Others may have 2 or more
  • Some have none (ducks, geese, penguins)
  • Create one by pulling out down feathers or have
    pouch-like flap of belly skin

25
Incubation Brood Patches
  • Present in sex that incubates, or both if both
    participate
  • Woodpeckers - male/night, female/day
  • Doves/pigeons - male/day, female/night
  • House Sparrow - male 10 AM-Noon only, female the
    remainder

26
Incubation Brood Patches
  • Some species, female only
  • Stay all night, leave periodically to feed
  • 60-80 nest attentiveness during day

27
Incubation Temperature
  • Usually 35C or higher
  • Higher temp. produces faster development, shorter
    incubation period

28
Incubation Period
  • Incubation period highly variable, no general
    trend
  • Larger birds tend to have longer incubation
  • Precocial species longer than altricial
  • Cavity nesters longer than open nesters
  • Examples bald eagle (both incubate) 35-46 days
  • Robin (female) 11-14 days
  • Bluebird (female) 12-14 days
  • House wren (female) 13-14 days

29
Hatching
  • Egg loses weight (evaporation, water loss)
  • Egg-tooth - top of beak tip
  • Hatching muscle - back of neck

30
Hatching
  • Used to chip circular hole out of large end
  • Pipping process
  • Chick spins around several times until it finally
    chips out

31
Hatching
  • Synchronized hatching may result from click
    communication among chicks in eggs
  • Accelerates/slows down development so all hatch
    at same time

32
Brood Parasitism
  • Origin?
  • Nest loss, using old nests, steal nests

33
Brood Parasitism
  • European Cuckoo
  • Time laying in other nests so other birds gone
  • Egg color, pattern matches host egg
  • Varies by region

34
Brood Parasitism
  • Shorter incubation period than host
  • Push out other eggs, nestlings
  • Aggressive begging

35
Brood Parasitism
  • N. Amer. examples
  • Brown-headed cowbird (obligate)
  • Redhead duck (strong tendency)

36
Brood Parasitism
37
Precocial Young
  • Eyes open
  • Down-covered
  • Leaves nest within day or two
  • Semi-precocial - stay at nest, fed by parents
    (e.g., gulls)

38
Altricial Young
  • Eyes closed
  • Naked
  • Unable to leave nest (fed by parent)
  • Semi-altricial - down-covered, stay in nest
  • Eyes open - hawks
  • Eyes closed - owls

39
Types of Young
40
Brooding
  • Altricial young must be brooded by parent to
    warm, dry them
  • Requires several days to develop endothermy
  • Direct all energy into growth

41
Brooding
  • Brooding reduced as young get older
  • Ceases within a few days

42
Feeding
  • Show precocial young the food, they feed
    themselves
  • Altricial young must be fed for varying times

43
Feeding
  • Monogamy - both parents feed
  • High-protein food - insects, animals (whole or
    part, regurgitated), crop milk

44
Feeding
  • Parents may have nest helpers
  • Older young, or unpaired birds waiting for
    opportunity to nest

45
Stimulus for Young to Beg
  • Begging begins in response to
  • Air currents
  • Vibrations of nest
  • Touch

46
Stimulus for Adults to Feed
  • Give food to young in response to
  • Cries, twitters
  • Head waving
  • Gaping mouths (yellow, orange, red, targets)

47
Trips for Food
  • Big foods - few trips per day
  • Small foods - hundreds or thousands of trips per
    day
  • Great parental energy expenditure
  • Weight loss, mortality

48
Sanitation
  • Dispose of egg shells
  • Predator protection
  • Eat, feed to young, dispose of

49
Sanitation
  • Fecal sacs
  • Covered by mucous membrane
  • Eat (undigested), or dispose of to keep nest
    clean

50
Nestling Period
  • Period of time from hatching to fledging
  • Great variation based on bird size, nesting
    habitat

51
Nestling Period
  • Longer in species with long incubation period
  • Longer in larger species
  • Longer in cavity nesters

52
Nestling Period
  • Great-horned Owl
  • Incubation 4-5 weeks
  • Nestling 4-5 weeks

53
Nestling Period
  • House Sparrow
  • Incubation 11-14 days
  • Nestling 15 days

54
Nestling Period
  • Downy Woodpecker
  • Incubation 12 days
  • Nestling 20-22 days

55
Nestling Period
  • Pileated Woodpecker
  • Incubation 18 days
  • Nestling 26-28 days

56
Nestling Period
  • Ends when young leave the nest
  • Still follow parents, may still beg for food
  • Eventually driven off by parents

57
Altricial vs. Precocial
  • Altricial start life behind precocial
  • Altricial catch up quickly and pass precocial
  • Eating machines
  • Altricial reach adult size more quickly
Write a Comment
User Comments (0)
About PowerShow.com