There are early signs that fewer lesser kestrels (above) and Amur falcons are visiting South Africa this year. (Photo by: Education Images/Universal Images Group via Getty Images)
While Andre Botha was driving back home to the Lowveld from Johannesburg this week, he noticed how few insects were splattered on his windscreen.
“I left at 3.30am and you would expect in the early morning, and the night especially, that there would be insect activity,” said Botha, the Vultures for Africa programme manager at the Endangered Wildlife Trust (EWT).
For him, this “grim” observation serves as a basic but accurate example of the reduction in the abundance of insects.
“In the 1970s, as a kid, you would drive in a car with your family and … within an hour or two, you would have to clean your windscreen because of the amount of insects that were killed on the windscreen. Now, you can drive for several hours and be lucky if there are a few blotches of insects,” he said.
This anecdote illustrates a bigger concern — the disappearance of insects and the threat this poses to migratory bird species.
The EWT has warned that the decline in insect numbers could cause food shortages for a range of species, not least the many insectivorous birds heading north from South Africa to Europe, the Middle East and Asia for the winter.
“We’re looking at lower availability of food for birds and obviously for migratory birds, particularly in areas where they do spend time. A lot of migrants come down here [Southern Africa] in our summer, and they do spend time here, but they are being affected by the availability of insects,” said Botha.
The theme for this year’s World Migratory Bird Day on 11 May was “protect insects, protect birds”, highlighting the relationship between migratory birds and insects amid alarming declines of both, according to the United Nations Environment Programme.
“Present in almost all the world’s ecosystems, insects are essential food sources for migratory birds on their long journeys,” the UN agency said. “Migratory birds often time their migrations to align with insect abundance. They [also] depend on these insects for food during migration stops and for breeding success and feeding their young.”
The stark reality uncovered in recent years is that the decline in insect populations correlates with a decline in bird species reliant on insects for survival. A 2020 analysis in peer-reviewed academic journal Science noted that 9% of the world’s insect population is being lost each decade.
Deforestation, industrial agriculture, pesticides, light pollution and climate change are major factors driving this trend worldwide, the UN agency said.
The United States and Canada have, for example, observed a significant 29% drop in bird populations since 1970, equating to about 2.9 billion fewer birds.
Although no official figures have been released yet, indications are that there have been fewer lesser kestrels and Amur falcons visiting South Africa this year, according to the EWT.
While insect declines may be a contributing factor, it may also be attributed to the fact that there was exceptional rainfall in East Africa, resulting in migratory birds remaining in areas of abundant resources instead of travelling further this summer.
Botha pointed out that in the past six to seven years, there was extensive drought in East Africa, “so the birds made landfall and then probably fairly swiftly moved south to where they would find food and where food was more reliable”.
“In the last year, East Africa — Ethiopia and Kenya — has had extensive rains. The conditions have improved there and obviously as a result food availability has certainly improved and that could play a role [where] rather than making their entire migration south, [the birds] could spend more time up there.”
Counts conducted by EWT field officers, particularly in the Northern Cape, North West, Mpumalanga and KwaZulu-Natal in January and February, range from thousands of falcons and kestrels in the Hanover area on 20 January to only a few hundred in the Standerton, Klerksdorp, Underberg, Victoria West and Beaufort West areas. Between 160 and 180 of the raptors were counted at De Aar in February this year.
These figures are still being collated for official publication.
The EWT said, too, that there may have been lower numbers of other species such as white stork in Southern Africa this past summer.
On the white storks, Botha said: “Again, there could be greater abundance of food further north, but what we also see now, particularly in southern Europe, is that many of these storks, rather than undertake the migration, they’ve adapted and started feeding on rubbish dumps.
“This is maybe partly because of the lesser abundance of their insect prey but it could also just be adapting what humanity and human actions do provide — a ready source of food even through fairly harsh winters in Europe.”
There’s no room for complacency, though. “One needs to consider that there are still reductions in insect populations, which doesn’t just affect the migratory birds but also the birds that are resident.”
Botha said some migratory bird species have “historical staging areas” where they spend time because of an abundance of food. “We’ve had areas that might have been suitable 20 years ago, but now no longer are” because they may have been modified by habitat change or climate change.
In some cases, bird species are adapting and adjusting to human-driven effects. “We’re seeing these phenomena in our own lifetimes, where some species adapt and they might cope and they might survive, but many others are probably less adaptable,” Botha said.
He was in Spain last week with colleagues who monitor migratory bird species, including small passerines (perching birds that make up more than half of all bird species) and large raptors, who told him of the declines they are observing.
“They say the numbers of species across the range has declined substantially. [Previously] they would have a ringing station that would in the morning catch and process 200 to 300 birds. Now they’re lucky if they catch 20 to 40 birds. Again, it’s an indication of a decline in numbers, which seems to be fairly consistent across species and taxa.”
Botha’s home in the Mpumalanga Lowveld borders on fairly intensive and extensive fruit farming. The use of pesticides has the knock-on effect of increasing bird and other insectivore mortalities, he said.
“The use of chemicals is pretty commonplace; it’s done and it happens and it’s used for a purpose to increase yields, but it does have an impact, not just on the crops and the pest organisms that they target, but most of these have a fairly broad impact on other species, obviously insects included, as a result.
“There is a change [in insect abundance] happening without a doubt, and in some areas, it’s not as severe, but definitely in areas where agriculture is practised, whether it’s subsistence or fairly intensive agriculture, the use of pesticides is really the driver of the decline in insect populations.”