GREAT SPOTTED CUCKOO
Thoughgreatspottedcuckoosalsoparasite
magpies,andothercuckoospeciesare
knownto expelanunpleasantsubstance
whenmolested,a protectiveeffecttowards
theirhostis unlikelyto begeneral.In
magpies,hostchicksstarveto deathintheir
veryfirstdaysoflife,dueto cuckoochicks
monopolisingallprovisioningeffortofthe
parents.Commoncuckoos,whichalso
produceananti-depredatorysubstance,
activelykillallhostnest-mates– ejecting
themfromthenestassoonastheyhatch. The
largersizeofcrowchicks,whichallowsthem
to bettercopewiththepresenceofa voracious
cuckoo,alsoenablesthemto benefitindirectly
fromitsself-defensivebehaviour,a situation
thatis probablyquiteuncommonamongall
broodparasite-hostrelationships.Greatspottedcuckoochicks
begveryvigorouslyandwill
outcompeteoneortwoofthe
smallestcrowchicksinthe
nestinthefirstfewdaysafter
hatching.However,afterthis
initialbroodreduction,crow
chicksrapidlyoutgrow
theparasiticnest-mate
andstartexploiting
itsintensebegging.In
parasitisednests,crow
chicksareabletobegless
vehemently(savingthem
energy)withoutsuffering
consequencesontheirfood
intake.Thisisbecausethe
intensebeggingbehaviour
ofthegreatspottedcuckoo
stimulatestheparents
tobringfoodtothe
nest.However,oncethe
parentsreturnwithvital
nutrients,theparasitic
chickcannotmanipulate
foodprovisioning,which is
distributedamongallchicks
presentinthenest.FINDOUTMORE Learnmoreabout
Daniela’sresearch:bit.ly/38padyJDANIELACANESTRARIisa
biologistandcurrentlylectures
attheUniversityofLeón(Spain).In Europe, there are only two species
of brood parasitic birds: the common,
cuckoo – which is found throughout
the Palearctic and parasitises a great
number of different host species –
and the great spotted cuckoo, which is
found in Southern Europe and Africa.
The great spotted cuckoo in Europe
is specialised on corvids – magpies
and carrion crows. Occasionally, it
can lay eggs in nests of jackdaws and
choughs. Other hosts, in its African
range, are hole-nesting starlings, pied
crows and black crows.of parasitism itself appears inadequate to
describe the connection between the great
spotted cuckoo and its crow hosts, which
may have more of a mutually beneficial
relationship than previously thought.
However, in years of very low predator
density, great spotted cuckoos are true
parasites for the crows – begging vigorously
so as to outcompete their nest-mates, leading
to considerable brood reduction and loss of
reproductive success for crows. But in years
when nest predators are abundant, and up
to 70 per cent of crow nests can lose all their
chicks, the presence of a cuckoo chick means
nests are more likely to be spared and at least
one crow chick is likely to fledge alongside
the parasite.
The outcome of the relationship fluctuates
between parasitism (when the parasite gains
and the host pays a net cost) and mutualism
(when both partners benefit), according
to the environmental conditions. This
may have prevented the evolution of
defences against the brood parasite in
this species.Moving in
Singing
for their
supper
Cuckoos have
evolved to produce
similar eggs to
their host species.