Vole + Raptor ecology

Question 1

Vole population density cycle

Answer 1

2-4 years (so our three years really does contain that change)

Question 2

Why did voles not move away from turbines?

Answer 2

This may be because although studies have found that voles may experience higher stress due to the noise and vibrations created by wind turbines (Lopucki et al. 2018), they are not necessarily less abundant near turbines. Lobucki and Mroz 2016 found that there was no difference in the characteristics of communities of small mammals near wind turbines and within control sites. They also argue that this could be due to habitat filling. Amherst island is an island and so even if primary habitat is filled up first by the voles, if there are many even the worse habitats will be filled up since there’s nowhere else to go. However on amherst we see a fluctuation in vole numbers so if this was the case i think we would have picked up of raptors changing their distribution.

Question 3

why are meadow voles on amherst special

Answer 3

it’s an island: so isolation and lack of terrestrial predators like foxes = intense population cycles

Question 4

Short eared Owl Hunting/food/predation

Answer 4

Small mammals, occasionally birds. strong correlation bw vole and owl abundance.
Hunts during day and night but are essentially crepuscular during the winter.
Courses area/hunts in flight like northern harriers. Prey detected primarily by acoustic cues but also sight. Slow flight speed and good agility, low noise
Predated by bald eagles, northern harriers and snowy owls

Question 5

Northern Shrike Hunting/Food/predation

Answer 5

In summer: arthropods mostly.
Winter: small mammals and birds.
voles are more important for these guys than loggerhead shrikes.
Hunts from open perches in shrubs or trees
Sits nd waits on exposed hunting perch, spot prey. attacks prey on or near ground by diving down from perch and flying fast to prey. Disarticulates cervical vertebrae. Carry vertebrates to special impaling or wedging structures so that they can pull it apart witht heir bill.
accipiters might eat them

Question 6

Bald Eagle Hunting/Food/predation

Answer 6

Likes live fish and waterfowl. Searches for prey by soaring, stoops to capture prey with feet
Are not generally predated as adults or even immatures

Question 7

Snowy Owl Hunting/Food/predation

Answer 7

will eat voles but also waterfowl
hunts during day unless weather is real bad. Sit and wait hunting technique. Rarely hover. Sometimes chase northern harriers and peregrine falcons.
Can be killed by eagles and hawks.

Question 8

American Kestrel Hunting/Food/predation

Answer 8

Small vertebrates.
Sit and wait (diurnal).
Locates prey visually from exposed hunting perches. Sometimes but rarely hover-hunt.
Might be able to find voles with urine trails bc of ultraviolet light reflected
Red-tailed hawks might eat them

Question 9

Red Tailed hawk Hunting/Food

Answer 9

Buteo
Mammals.
Done from elevated perch, looking for prey. Sometimes flap and glide.

Question 10

Rough-legged Hawk Hunting/Food

Answer 10

Buteo
Mostly lemmings and voles.
Waits on perches (especially in winter), may hover in flights. Sometimes crepuscular. Mostly sight

Question 11

Northern Harrier Hunting/Food/predation

Answer 11

Mostly voles in the winter.
Hunts on the wing, coursing low.
Prey hunt successful with snow cover, but challenging when ice is covering the snow making it harder to pounce and to hear prey.
Use sound if there are no visual cues (has similar facial disc as owls).
can get killed by owls

Question 12

Short eared Owl abundance trends why/distribution

Answer 12

Less snow cover makes hunting easier because of hunting methods

Question 13

Northern Shrike abundance trends why/distribution

Answer 13

Stay the same

Question 14

Bald Eagle abundance trends why/distribution

Answer 14

Territories can be large, average in winter about half the size of amherst.
Increase. After ban of DDT. Also as climate change worsens, northern migrants may not travel as far south in winter months which may appear as an increasing pop trend in more northern regions. Also high vole year in 2019 (post-turbines).

Question 15

Snowy Owl abundance trends why/distribution

Answer 15

Decrease. Believed to be declining. also large year pre-turbines in 2015. also potentially avoiding bald eagles?

Question 16

American Kestrel abundance trends why/distribution

Answer 16

stayed the same. Most abundant north american falconiform

Question 17

Red-tailed Hawk abundance trends why/distribution

Answer 17

Higher after construction.
Replaced red-shouldered hawk a lot in cleared forests. Expanded in north america from forest clearing for agriculture. Winter densities are greatest where snow cover is minimal and prey density is high. Also as climate change worsens, northern migrants may not travel as far south in winter months which may appear as an increasing pop trend in more northern regions. Also high vole year in 2019 (post-turbines).

Question 18

Rough-legged Hawk abundance trends why/distribution

Answer 18

No changes

Question 19

Northern harrier abundance trends why/distribution

Answer 19

Higher. Prey hunt successful with snow cover, but challenging when ice is covering the snow making it harder to pounce and to hear prey which we’re not seeing anymore.

Question 20

Short-eared owl behaviour/habitat

Answer 20

open areas but will sometimes be in trees.

Question 21

Northern Shrike behaviour/habitat

Answer 21

stay near open edges of forests, wetlands, plains. In the winter often choose similar areas as american kestrels

Question 22

Bald Eagle behaviour/habitat

Answer 22

Food availability was basically the main thing for them

Question 23

american kestrel behaviour/habitat

Answer 23

open habitats with short ground vegetation

Question 24

Red-tailed hawk behaviour/habitat

Answer 24

Semiopen areas with perches. Lots of grassland/agricultural lands with scattered trees. Sometimes gather in small groups in the winter

Question 25

Rough-legged hawk behaviour/habitat

Answer 25

Grasslands. Compete with other buteos.

Question 26

northern harrier behaviour/habitat

Answer 26

In winter, females defend territories. (0.65km2). Sometimes displaced by other larger raptors.
Open areas
Sometimes communal roosting

Question 27

snowy owl behaviour/habitat

Answer 27

Will form communal roosts in the winter.

Question 28

Why bald eagles don’t show diffs in age around turbines unlike white-tailed eagles at smola windfarm

Answer 28

Smøla = 68 turbines (huge)
White-tailed eagles are all studied in norway
The way the turbines are laid out is different: lines vs little pockets which have been shown to possibly cause more displacement. If habitat is affected more by this type of windfarm, its possible that territorial adults have been displaced and subadults see locations around turbines as good territory.
Study was done during early breeding season too, which may lead to different results than wintering birds.’
One study found they were both displaced .
Finally, adult white-tailed eagles at smola are resident birds, while juveniles move away from smola during summer and autumn to the north and return for breeding season. Perhaps this difference in abundance throughout the year leads to different types of territoriality, where adults are more established overall. Also as there are vacant territories surrounding the area where eagles used to breed, perhaps younger ones are able to get established there.