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Mar 377 > Diet and Foraging Behavior > Flashcards

Diet and Foraging Behavior Flashcards

1
Q

What is a seabird diet composed of?

A
  • Fish
  • Squid
  • Invertebrates
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2
Q

What are foraging fish?

A

Pelagic schooling fish

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3
Q

Why are forage fish important to marine ecosystems?

A

They represent a link between primary and secondary producers as well as top predators

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4
Q

What are the three main habitats that seabirds forage in?

A
  1. Coastal
  2. Diving: exploit depths to gather food
  3. Pelagic: explore vast expanses of the ocean in search of prey at the surface
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5
Q

What are the four main feeding methods of seabirds?

A
  1. Aerial predators
  2. Pursuit divers
  3. Surface feeders
  4. Plunge divers
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6
Q

Describe aerial predators

A

Steel food from other birds (kleptoparasitism)

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7
Q

Describe surface feeders

A

Peck or grab prey items from at or below the surface (while sitting on the surface or on the wing)

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8
Q

Describe plunge divers

A

Dive from high altitude and utilize the momentum from the dive to move underwater

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9
Q

Describe pursuit divers

A

Pursue prey from substantial distance by swimming underwater (penguins)

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10
Q

Describe Phalarope spinning

A
  • Spinning creates upwelling
  • Prey items = drawn closer to the surface
  • Only works in shallow water
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11
Q

When do seabirds feed?

A
  • Daytime (most seabirds)
  • Nighttime (Squid eaters ex: albatrosses, gadfly petals etc.)
  • Dawn / Dusk (Common murres etc.)
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12
Q

Describe diel foraging patterns

A
  • Refers to the vertical migration of prey
  • Prey = down deeper in the day and closer to the surface at night
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13
Q

What is a possible cause of diel foraging patterns?

A

Prey species could be attempting to avoid visual predators at the surface during the day

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14
Q

Describe the foraging patterns of Red-legged Kittiwakes

A
  • Forage at night on vertically migrating prey
  • Surface feeders (feed on myctophids)
  • Feed on prey when its closer to the surface
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15
Q

Why do species such as penguins not rely on diel patterns?

A

They are deep divers

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16
Q

What other factors drive the timing of foraging?

A
  • Flood tides (more birds tend to forage during the ebb-tide)
  • Breeding seasons (foraging trips = longer during brood-guard / chick rearing stages)
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17
Q

Why do many seabirds associate with sub-surface predators?

A

Sub-surface predators help drive prey to shallow depths

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18
Q

What seabird species are closely associated with sub-surface predators?

A
  • Brown noddies
  • Wedged-tailed shearwaters
19
Q

How can we study what seabirds eat?

A
  • Direct observation
  • Studying what prey is brought back to the nest
  • Examining stomach contents
  • Tissue analysis (blood samples)
20
Q

What are the pros and cons of direct observation of seabird diets?

A

Pros:
- Easily collected (bird must be in sight)
Cons:
- Only useful for surface feeders
- Expensive, labor intensive
- Small number of observations

21
Q

What are the pros and cons of studying regurgitates?

A

Pros:
- Easily collected (when bird is present)
Cons:
- Biased (different prey types have different digestibility)
- Only recent diet is reflected in the sample

22
Q

What are the pros and cons of studying prey that is dropped near the nest?

A

Pros:
- Provides information on recent diet
Cons:
- Biased towards larger spiny deeper bodied prey
- Contain high proportions of refused prey items

23
Q

What are the pros and cons of studying prey that is carried in the bill?

A

Pros:
- You can estimate the size and mass of the prey item
Cons:
- Useful for identifying prey items fed to chick but not adults
- Relies on remote observation

24
Q

What are the pros and cons of studying seabird stomach contents?

A

Pros:
- Can give detailed understanding of seabird diet
Cons:
- Biased towards prey with “hard parts”
- Only most recent prey items can be assessed

25
Q

How can seabird diets be categorized?

A

Through bones ex:
- Otoliths: inner ear bones of fish
- Squid beaks

26
Q

How can Nitrogen isotope analysis be used to study seabird diets?

A
  • Nitrogen signature = enriched (3-4%) at each step in the trophic scale of the food web
  • Nitrogen isotope ratio = used to estimate trophic position of prey
27
Q

How can Carbon isotope analysis be used to study seabird diets?

A
  • Carbon 13 = used to differentiate nearshore production (from algae) and pelagic production (from phytoplankton)
28
Q

What are the pros and cons of studying seabird isotope analysis?

A

Pros:
- Can infer relative trophic position of different species
- Can examine diet over long time periods
Cons:
- Costly, time consuming

29
Q

How can fatty acid analysis be used to study seabird diets?

A

Different prey types have unique fatty-acid signatures that can be found within its tissue “you are what you eat”

30
Q

What are the pros and cons of studying prey fatty acid analysis?

A

Pros:
- You can examine the diet of a seabird over weeks-months
Cons:
- Costly, time consuming

31
Q

What conservation issues do seabird dieting and foraging habits face?

A
  • Depredation
  • Fishery Discards
  • Fishery Bycatch
  • Marine Debris
32
Q

Depredation

A
  • Raid on a fishery
  • Could lead to entanglement in fishing gear or death
33
Q

Fishery discards

A
  • Fisheries discard unwanted catches
  • Seabirds become dependent on discards
34
Q

Fishery Bycatch

A

Seabirds can get cough in fishing equipments and then discarded in the bycatch which consists of all the animals that the fisherman do not want

35
Q

What is a life cycle?

A

A series of developmental changes (life stages) throughout an individuals life

36
Q

What are the different life stages in seabirds?

A
  1. Egg
  2. Chick
  3. Fledgling
  4. Juvenile
  5. Adult
37
Q

What life stages have the longest periods of time between them?

A

Juvenile to adult

38
Q

Describe the duration of incubation periods?

A
  • 20 days (small terns)
  • 80 days (albatrosses)
39
Q

Describe the duration of nestling periods?

A
  • Hatching until fledging
  • 2 days (alcids)
  • 1 year (king penguins)
40
Q

Describe the duration of post-fledgling care

A
  • 1 month (alcids)
  • Several months (frigatebirds and boobies)
  • None (penguins, albatrosses, puffins et.)
41
Q

During what stages of life are seabirds mostly in in coastal or pelagic environments?

A

Juvenile to adult stages

42
Q

During what stages of life are seabirds mostly in the breeding colony?

A

Egg, Chick, Fledging

43
Q

Describe the breeding cycle of the Southern Royal Albatross

A
  1. Pre-egg stage (mating: early October)
  2. Egg laying (late October-November)
  3. Incubation and hatching (December / January)
  4. Guard stage (February / March)
  5. Post-Guard. stage (fledging: April-August)

Mar 377 (16 decks)

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