Seasonal Update - October 2019


Autumn got off to a chilly start with the UK under the influence of a northerly airflow that brought with it a polar maritime air mass, causing temperatures slightly below where we’d expect for the time of year. It was 1C at dawn on the 8th September, even down here in the New Forest on the south coast. This cold snap was short-lived, however, and a couple of low pressure systems swept across us in the second week of the month, bringing rain and, particularly along the western fringes, gale force winds.

With everything happening in British politics in the last few weeks, some readers may be forgiven for having switched off the news and social media. Those who didn’t probably heard about hurricane Dorian devastating the Bahamas before cutting a path of destruction along the eastern seaboard of the United States and Canada. Dorian, an extremely powerful and long-lived Category 5 storm, developed from a tropical wave over the central Atlantic on 24th August and intensified rapidly as it travelled towards the Lesser Antilles. The hurricane made landfall in the Bahamas on 1st September, bringing 295 kmph (185 mph) winds and catastrophic storm surges that flattened and flooded buildings, felled trees and killed at least 50 people. At the time of writing, the damage is estimated to be in excess of $7 billion. Hurricane Dorian was the strongest storm ever known to have hit the Bahamas and scientists think that rising sea temperatures are going to make such extreme weather events more common.

Hurricanes, such as Hurricane Ike pictured captured here by the International Space Center over Cuba in September 2008, are predicted to become more severe as our climate continues to change. - Credit: NASA Johnson (CC BY-NC 2.0)

Dorian was particularly devastating because it stalled; at one point it slowed to just one mile per hour. The result was that it took 18 hours to cross the Bahamas, which is a long time to be exposed to such powerful winds and torrential rain – 60 cm (24 inches) according to rainfall figures released by NASA last month. The phenomenon of hurricanes stalling appears to be increasingly frequent in recent years and meteorologists think it’s a result of warming seas.

Hurricanes begin life as small clusters of thunderstorms. Wind blowing over the ocean causes water to evaporate from the surface and rise into the atmosphere where it cools, condensing into thunder clouds. Under warm conditions, cooler and drier air is sucked in to replace the warm, moist air, forming a “tropical depression”. As the storm travels over warm water it sucks up more warm and moist air, which gets pushed to the edges of the system where it picks up yet more moisture. The result is a positive feedback loop. Consequently, the storm rapidly intensifies into a hurricane and the more warm water it travels over, the bigger (i.e. more powerful) it gets. Warm air also holds more moisture than cold air, meaning these hurricanes can drop a lot of rain when they make landfall and start to cool. Dorian underwent rapid intensification twice on its journey to the Bahamas and scientists think that while our oceans warming won’t mean we see more hurricanes than normal, we will see an increase in powerful Category 4 and 5 storms.

After a north-south split in the UK’s weather for the first half of the month, wet in the north but dry in the south, high pressure built in and brought a brief “Indian Summer” for mid-September, with temperatures in the low 20s Celsius before ex-hurricane Humberto brought thunderstorms, wind and rain for the final week.

As October gets underway, the weather models are predicting largely mild and dry conditions for the first half of the month, before we may see low pressure systems sweeping in off the Atlantic, bringing some much-needed rain to England. If you’re up for getting outside for autumn, as usual, the Wildlife Trusts have a series of nature-themed events up and down the country, as do the RSPB. If you feel like being proactive this month and live near the coast, Surfers Against Sewage is looking for people to organise cleans of their local beaches – details here. The Forestry Commission is running a series of events this month – full list here.

Interested in the wildlife to be found this month? Check out my Wildlife Watching - October page. Elsewhere on the site, a new section discussing play behaviour in squirrels and a new QA on the subject of keeping squirrels as pets.

Honeybees pick up neonicotinoids from farm weeds

Many readers will be familiar with a class of insecticides used on many crop plants known as neonicotinoids and the concerns that have been raised over the potential detrimental impact they can have on pollinators, bees in particular. Generally speaking, “neonics” are low toxicity to birds and mammals, but potently toxic to insects, and their use has been linked to such phenomena as colony collapse disorder in the USA. Despite concerns, in 2014, virtually all corn planted in the US was treated with one of two neonic insecticides, while about one-third of US soy beans were grown from neonic-treated seeds. In 2018, the EU restricted use of some neonicotinoids and the US has since restricted their use in some areas, although they remain the most widely-used insecticides in the world.

Bees visit flowers within a wide area of their hives and can be exposed to pesticides on both target and non-target crops. - Credit: Marc Baldwin

A significant issue with neonics is that it’s not only the compounds themselves that are toxic to insects, so too are some of the breakdown products. Furthermore, neonicotinoids are water-soluble, allowing them to enter water sources and be taken up by plants growing outside the application zone and incorporated into their pollen. Indeed, a recent collaborative study by entomologists in Indiana has found that agricultural “weeds” potentially expose pollinators to more neonicotinoids than the crops that have been sprayed. To better understand the potential for bees to pick up these insecticides from non-target plants, a team of researchers led by Tom Wood at Michigan State University spent two years studying neonicotinoid residues in pollen collected by commercial honeybee colonies released in 24 areas of the state to pollinate pickling cucumber crops.

The honeybees collected a total of 40 pollen types from 22 families of plants. About 61% of the pollen was collected from herbaceous plants (mostly goldenrod and sowthistle), 29% from crops (mostly maize) and 10% from woody plants (primarily sumac). Concerningly, the researchers found that neonicotinoids were consistently identified in pollen, with 96% of all samples containing clothianidin, imidacloprid or thiamethoxam. In particular, higher clothianidin and thiamethoxam residues were associated with pollen collected from agricultural weeds. Indeed, despite being directly treated with insecticide, comparatively little contaminated pollen was collected from the cucumber plants, while much more was collected from herbaceous non-crop plants in the vicinity of the cucumber fields. Writing in the Proceeding of the Royal Society, Wood and his colleagues urge swarm owners to think carefully about the placement of their hives:

Our results suggest that neonicotinoid exposure rates, and hence the overall risk that these compounds pose, have the potential to be highly variable and dependent on the environments in which apiaries are located for the full duration of their foraging period.

Honey bee collecting pollen. - Credit: Marc Baldwin

These results also suggest that other pollinator species may be unintentionally exposed to insecticide when foraging in set-aside strips, on banks and in ditches near agricultural fields where neonicotinoids are applied.

Reference: Wood, T.J. et al. (2019). Honeybee dietary neonicotinoid exposure is associated with pollen collection from agricultural weeds. Proc. Roy. Soc. 286B (1905): 20190989.

Can staring down sea gulls save your chips?

The sense of being watched is the greatest fear night animals have” was the sales pitch used by the manufacturers of a fox and cat repellent device on their website. The premise being that this device had a couple of LEDs that were intended to give foxes and cats visiting your garden the impression they’re being watched. While this company’s monologue was an exaggeration, many of us are uncomfortable if we feel we’re being watched and familiar with the expression “if looks could kill”, alluding to the ancient superstition that some people possess a “demonic power” through which they can kill another person with just a stare – the fabled “evil eye”. In South America, it is said that the stare from a jaguar is enough to cause monkeys to fall from the trees. Similar apocryphal abilities are attributed to leopards in Africa.

Chips on the beach is a favourite holiday pastime for many Brits, but in many coastal towns holidaymakers need to be on their guard for gulls. - Credit: Kathryn Wright (CC BY-ND 2.0)

While it may take more than a couple of LEDs to stop a fox or cat crapping on your lawn and heart attacks likely explain falling monkeys, many animals do appear to share our dislike of being stared at. In many of our coastal towns, gulls, specifically herring gulls (Larus argentatus) are increasingly seen as a nuisance, particularly during the summer months when they’re rearing chicks. Many councils urge visitors not to feed the birds and in 2014, councils in Exmouth, Sidmouth and Seaton in Devon shelled out £15,000 to hire peregrine falcons to scare away gulls from some popular beaches. There’s a limit to the action councils can take, however, because all gulls are protected under the Wildlife and Countryside Act (1981), which prohibits people causing deliberate interference, injury or death – for good reason, too, as the UK population has declined by an estimated 60% since 1969.

One common complaint of herring gulls is that they’re adept at stealing food from holiday makers and anyone who has spent time on West Country beaches knows to guard their chips with military diligence. New research from the Centre for Ecology and Conservation at the University of Exeter suggests, however, that the “hard stare” familiar to all Paddington Bear fans may be enough to keep the birds away from your seaside snacks.

A team of biologists, led by Madeleine Goumas, laid out portions of chips in Cornish coastal towns during November and December 2018 and assessed how the approach behaviour of herring gulls was affected by the activity of an observer sitting about 1.5m (5ft) away. The researchers attempted to test 74 birds, but not all of them were equally interested in the experimental setup, illustrating how a gull’s probability of being a “nuisance” varies according to the individual. In the end, 19 birds completed both trials, during which they were subjected to two “treatments”; one where the observer stared at the gull as it approached the food, and the second during which the observer continued to look away as the bird approached.

Goumas and her colleagues found that gulls took significantly longer to approach food when they were being watched; the presence of other people and other gulls also increased the approach time. On average, gulls took 22 seconds longer to approach the food when being looked at than when the observer’s gaze was diverted, but in some cases it took five minutes for the bird to approach (versus a maximum of just under three minutes when they weren’t being watched). Writing in the journal Biology Letters in August, the researchers explain:

“... our results indicate that the majority of urban herring gulls are unlikely to approach food when humans are nearby. Those gulls that did approach responded to subtle behavioural cues from the experimenter, suggesting that increased vigilance by humans may reduce food-snatching behaviour.”

New research by the University of Exeter suggests that making direct eye contact with gulls can slow or even stop their approach to food. - Credit: Marc Baldwin

Reference: Goumas, M. et al. (2019). Herring gulls respond to human gaze direction. Biol. Lett. 15: 20190405.

Related reading