BBC Wildlife - UK (2020-08)

August 2020

WILD NEWS

Henry Pollock

Whenabelovedtree

toppledspectacularlyathis

eldsiteinPanama,Henry

Pollock’sdisappointment

quicklyturnedinto

excitementaboutanew

anduniqueopportunityto

studyavarietyofspecies.

Researchassociate,UniversityofIllinoisatUrbana-Champaign

MEET THE SCIENTIST

T

he toppling of a

giant – whether

it’s King Kong, an

elder statesman or

a decommissioned

cooling tower – is

likely to bring a lump to the throat.

So it was when a huge tree fell in

a patch of Panamanian rainforest

used by generations of University of

Illinois biologists to assemble one

of the longest-running bird-netting

surveys in tropical America.

As it happens, no one was around

to hear the emergent tree fall, but on

the evidence of the hole it rent in the

fabric of the forest, the noise would

have been considerable.

“It took a bunch of other trees

with it, wiping out a huge swathe of

about 2ha,” says ornithologist Henry

Pollock. He describes the reaction

ofhisseniorcolleague,JeffBrawn,

whentheyinspectedthedamage:

“Hewascrestfallen– reallyupset

outit.Hesaid‘Oh,

an,I’vebeen

lkingpastthis

for 30 years,

now

gone.’”

when they stumble upon a gap with

their preferred food sources – nectar

and fruit – they stay put.”

But not for long. “Within a year for

the hummingbirds, and within three

years for the frugivores, they’d gone

again,” Pollock says. “These gaps are

really useful for the forest, but they

are ephemeral, so regular ecosystem

disturbance is essential if these birds

are to persist in the landscape.”

The biologists’ foray into the

ecology of treefalls was also short-

lived – a case of right time, right

place. The routine netting, ringing

andmonitoringoflong-term

populationtrendscontinues,though

COVID-19is nowmakingeventhat

farfromstraightforward.

Whiletravelrestrictionsarein

place,Pollockis workingona paper

aboutthelongevityofrainforest

birds,somethingthatis onlypossible

becauseofthelong-termnature

oftheiruniquedataset.“Wecatch

thesamebirdsoverandoveragain,”

saysPollock.

Meanwhile,there’snotmuchleft

ofthefallengiant.“Thathadmostly

goneaftertwoyears,”saysPollock.

“Stuffgetsrecycledreallyfastin

thetropics.”StuartBlackman

Onespecieshadn’tbeen

caughtbeforeduringthe

projectandyetwenetted

16 ofthemwithindays.

S

T

But ends are also beginnings:

“It turned out to be a unique

opportunity,” says Pollock. “We

carried on with the netting routine,

and started catching all these

hummingbirds. One species, the

snowy-bellied hummingbird, had

neverbeen caught before during the

entire44 years of the project, and yet

wenetted 16 of them within days.”

Overall, the total diversity of

hummingbirds caught at the site

morethan doubled. Frugivorous

birds,such as red-capped manakins,

alsoincreased.

Thesudden loss of the canopy

f dedthe understory with

ht, creating conditions

r species to flourish,

wer and fruit.

“Itallhappens pretty quickly,” says

Pollock.“It seems that the birds are

prospecting around the forest and

ReadHenry

Pollock’s treefall

research in the

Journal of Field

Ornithology

bit.ly/3hxt2UK

To p t o b o t t o m : C l a i r e J o h n s o n ; J o h n A n d r e w s ; M i c h a e l & P a t r i c i a Fo g d e n / M i n d e n / N P L

FIND OUT

MORE

Pollock ringing a

white-bellied antbird.

Bottom left: a snowy-

bellied hummingbird.