It is interesting to see how Peregrines are so well suited to life in
the concrete jungle.
http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2008/02/06/eapereg106.xml
Peregrine falcon adapting to urban lifestyle
By Brian Unwin
Last Updated: 1:01pm GMT 06/02/2008
The peregrine falcon is becoming a night hawk. The swiftest and
deadliest of all avian predators is increasingly being seen soaring
across city centre skylines and nesting in high rise blocks.
And it has developed a different killing technique to go with its new
urban lifestyle.
The falcon, famed for its 100mph stoop, is becoming nocturnal - using
the glare from illuminated buildings to spot its prey - and the
shadows they throw up as cover for its deadly ambush.
With tall buildings offering ideal nest sites and feral pigeon
populations ensuring an ample food supply, there were clear advantages
in the peregrine moving from the countryside to the city.
Floodlit buildings have provided new opportunities with night-flying
birds and even bats now very much in the peregrine's sights.
"Evidence of nocturnal hunting behaviour illustrates just how well
adapted peregrines are to the urban environment", says a report in the
new edition of the journal British Birds.
Studies in France, Germany and Holland tell how they "use artificial
light directed on to buildings at night to their advantage, attacking
prey at short distances and using the shadows to avoid being dazzled
while looking for a potential kill."
Investigations in Berlin and New York found that during the peak
migration period of potential quarry species, peregrines were not seen
to be hunting until after sunset.
In Taiwan, peregrines are known to use a tall bridge tower that is lit
up at night. Filming of their nest site revealed that almost 80 per
cent of 44 prey item recorded were brought in after dark.
A peregrine food cache on an industrial chimney in Holland consisted
of hundreds of birds - mainly moorhens, water rails, teal (Europe's
smallest duck) and snipe - stored for later feeding, the report adds.
"The site, illuminated at night, is on a main migration route for
these species and it is thought that they were probably taken at night
while on passage."
Direct observations from New York's 1,250ft high Empire State Building
found peregrines "regularly hunting nocturnal migrants such as yellow-
billed cuckoo and Baltimore oriole.
"The presence of at least three peregrines at any one time was
significantly more likely on evenings when more than 50 migrants were
counted passing over during the night."
Artificial lighting can cancel out the natural camouflage of prey
species' plumage, explains the report by Edward Drewitt of Bristol's
City Museum and Art Gallery, and Nick Dixon.
For instance waterbirds with dark upperparts and pale undersides are
camouflaged from aerial predators while swimming - but not if flying
at night in artificially illuminated areas.
"Under such conditions, pale underparts are strikingly obvious from
below, while peregrines perched on high vantage points will see low-
flying migrants as dark silhouettes against the illumination."
However, modern lighting in towns may have simply helped them develop
night-hunting abilities they already had as the report also gives
examples of prey being taken after dark in unlit wild locations.
For instance, off American north Pacific coasts, peregrines are known
take seabirds such as fork-tailed storm-petrels, ancient murrelets and
Cassin's auklets at night or during twilight.
They have also been recorded trying to catch bats at cliff sites in
Northern Ireland. Radio-tracking of birds fitted with tiny
transmitters has indicated flying and possibly hunting at night in
Somerset.
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