how birds forage

Question 1

importance of nutrients

Answer 1

require both micro (vitamins, ions, amino acids) and macro (protein, carbohydrates, fats and water) nutrients
low in calcium: low clutch size, eggs fail to hatch, small brood size or abandoning nests

Question 2

plant exudate eater

Answer 2

exudativores (e.g. sapsuckers)

Question 3

all food eater

Answer 3

omnivores (e.g. crows, gulls)

Question 4

animal flesh eater

Answer 4

carnivores (e.g. falcons, vultures)

Question 5

fruit eaters

Answer 5

frugivores (e.g. hornbills, toucans)

Question 6

grass eater

Answer 6

graminivores (e.g. geese, swans)

Question 7

seed eater

Answer 7

granivores (e.g. finches, sparrows)

Question 8

insect eater

Answer 8

insectivores (e.g. swallows, wrens)

Question 9

fish eater

Answer 9

piscivores (e.g. cormorants, the Osprey [Pandion haliaetus])

Question 10

niches

Answer 10

foraging niches are formed due to digestive machinery and specialised feeding behaviours.
reducing competition with others of the same species (or conspecifics) and with birds of other species (or heterospecifics).

Question 11

specialised foraging charecteristics

Answer 11

bills, feet, digestive machine and behaviours specialised based on diet

Question 12

specialised bill examples: flamingo

Answer 12

flamingo: suck water into mouth cavity and force it out side of the bill to collect macroinvertebrates on sieve elements and tounge onto bolus (all of food)

Question 13

specialised bill examples: wader bills

Answer 13

example of niche separation
wetland birds consume different prey across the inter tidal zone. e.g. turn stones have a robust bill to turn stones. whimbrel have very long bills to insert into sand and very touch sensitive. oyster catchers reduce competition by nocturnally foraging. divided into two groups: hammer and pryers

Question 14

birds and speciation Darwin’s finches

Answer 14

niche separation
adaptive radiation on the Galapagos islands.
wide range of food types by using bills to extract: termites, insect, blood, egg, fruit, pollen, leaves etc

Question 15

specialised feet

Answer 15

feet are generally specialised for locomotion
however feet in Osprey are use for feeding and hunting fish bellow the water surface.

Question 16

specialised leg

Answer 16

gymnogene (African Harrier-hawk)
can disarticulate the lower leg to fir into rocky cervices to hunt down reptiles.

Question 17

specialised gut

Answer 17

there are varying degrees of specialisation of gut component
- crop: pouch for collecting food
- stomach: separate proventriculus (mechanical digestion) and gizzard (chemical digestion
- Caecum: specialised to extract as much energy as possible
- cloaca and vent

Question 18

crop variation

Answer 18

chamber at top of digestive tract
large diversity across species.
meat eaters store less food because food is nutrient rich.
larger crop for less nutrient rich food or rapid consumption of food e.g. vultures.
pigeon crop is large possibly due to production of crop milk for young

Question 19

the avian ‘stomach’

Answer 19

two separate structures.
glandular proventriculus secretes pepsin, HCl and mucus when food arrives from oesophagus.
muscular gizzard is avian equivalent of teeth. mechanical part of digestion to grind food.
gizzard is better developed in birds that eat hard items

Question 20

caecum

Answer 20

voluminous to absent depending on species
developed in herbivores and omnivores
in closely related species (e.g. ducks) caeca developed in true herbivores and tiny in piscivores
over two-thirds of avian species have small or non-existent caeca

Question 21

cloaca and vent

Answer 21

eggs made and faecal matter from same structure .
lips close over during egg laying so male sperm doesn’t mix with female waste product.

Question 22

specialised behaviours

Answer 22

enables to occupy a specific niche e.g. skimming
- detects pray through touch
- upper mandible shuts when fish is detected
- instantaneous response

Question 23

specialised behaviour: ambush

Answer 23

used by many birds of prey
e.g. Verreaux Eagle attacks Rock Hyrax when sunning on a rock

Question 24

specialised behaviour: pursuit

Answer 24

e.g. sawbill duck pursue fish under water: swallow fish head first to avoid spines
serrated bill allows slippery fish to be caught

Question 25

specialised behaviour: plunge diving

Answer 25

used by all pelcaniformes
e.g. brown pelican tucks wings behind themselves before diving downwards for efficiency

Question 26

specialised behaviour: hooding or canopy feeding

Answer 26

foraging technique of caniiformes
covers entire body in outstretched wings
- lulls fish into thinking it is in a safe rocky outcrop
- protects birds eyes from sun for better sight

Question 27

specialised behaviour: Ossuaries

Answer 27

flat rock used to fragment bones
used by Lammergeier or Bearded Vulture
drops whole skeletons because 85% of its diet is bone
also done by crows

Question 28

specialised behaviour: larders

Answer 28

acorn woodpecker
nut specialised
can store up to 50 000 acorns per year
highly territorial of their larders
also used by red back strike to tenderise meat before consumption

Question 29

tool use

Answer 29

song thrushes use anvils: use pebbles to bash snails.
New Caledonian Crows make tools from twigs, cardboard and wire to complete foraging tasks

Question 30

specialised behaviours: milk bottle tops

Answer 30

Blue and Great tits learnt to open foil bottle tops to feed on cream
this is an example of cultural transmission as the skill was learnt by other birds and spread across the UK.
this is due to high brain to body mass

Question 31

specialised behaviours: hunt in packs

Answer 31

pelicans fish co operatively and drive fish to shallows and use a barrage of bills so fish cant escape.
Harris Hawks hunt jack rabbits as many pairs to exhaust the rabbit.

Question 32

some calcium sources for birds

Answer 32

snail eggs
eggshells
vertebrate bones
ash
soil
clam shell
decaying wood
calcium-rich fruits