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The fires
in the Outeniqua Mountains around George (Western Cape province, South Africa)
that raged from the end of October to beginning of November 2018 were the
largest in the region in recorded history, burning a region of some 80 000
hectares, leaving 8 people dead and many people homeless. These fires follow
close on the devastating Knysna fires of 2017. Fighting fires in these remote
mountain areas is dangerous: one helicopter pilot died during the most recent
incident, and fires are generally only engaged with they threaten people or
property. For weeks we were on fire alert, fire fighting equipment at the
ready, as we woke to smoke-filled valleys from the fires from the adjacent
mountain range.
Still, the
vegetation of these mountains, Fynbos, is fire adapted, with many species
requiring a fire event as part of their life history strategies, either to
clear away dominant vegetation in the case of rapidly resprouting geophytes and
grasses, or to release seed stocks stored on the plant over years, as in the
case of most protea species. Similarly, bird communities change in response to
fire history, with terrestrial foraging insectivores and granivores dominating
recently burned veld, whereas nectarivores dominate older vegetation. So, while
fire might be great news if you’re a Cape Rockjumper or Long-billed Pipit, it’s
bad news if you are an Orange-breasted Sunbird or Cape Sugarbird. These
nectarivores require flowering Erica
and Protea species for most of their
energy requirements, and these plants normally only start to flower a few years
after a fire event. What happens then, to these birds after a fire?
I have been
ringing on Blue Hill Nature Reserve, Western Cape, about 2 hours drive from
George, since 2011. Back then, there had not been a fire on most of the
property for some 15 to 25 years: tall proteas crackling with Cape Sugarbirds
dominated the landscape. But at the beginning of 2012 a massive fire swept
across most of the property. Predictably, the sugarbirds and sunbirds
disappeared, but had they died or departed? I would retrap only two birds that
had moved to an adjacent unburnt valley, so what had become of the rest? I
could only speculate.
However,
just after the Outeniqua fires I was bird ringing again near a pond where I was
expecting to mostly catch granivorous species like Cape Siskin and Cape Canary
that come to drink. Instead, my nets were literally sagging with
Orange-breasted Sunbirds. Closer inspection would reveal that the majority of
these were also young birds: only a few months old and displaying residual
gape, or with some youngsters with an orange feather or 2 giving away that they
were aspiring to be beautiful males. The sheer quantity was overwhelming: on 14
November 2018, in 3 hours I caught 47 Orange-breasted Sunbirds from a total of
67 birds using a single 12-meter-long net. The huge number of birds could not
have originated on the reserve, they must have come in from the burnt areas to
the south. Certainly, for a bird traditionally associated with Erica species,
there were none to be had at this ringing location: they may instead have been
settling for muddy water and blue Psoralea
flowers (members of the Fabaceae).
On average,
these birds were also the lightest compared to the previous 3 years, indicating
some birds may have been starving. One was soon recovered dead, and by the end
of December, capture rates had declined dramatically – the birds likely
dispersing further or dying. Certainly, there were no refugee camps for these
youngsters. Overall though, a cruel reminder of the impacts of increasing fire
events in the fynbos and the consequences for its wildlife.
By comparison Cape Weaver capture rates are 'the same'
The proportion of 'juveniles' is alarmingly high
Female capture mass of the young birds especially was very low, and male capture mass lower than generally recorded. Note, females weigh less than the males.
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