City Nature Challenge: Species to Spot | Citizen Science

There are so many ways to take part in City Nature Challenge it can be difficult to know where to start if you are new to observing nature. Observations of any living things count towards City Nature Challenge but here are six species that Museum scientists and friends are particularly interested in. If you see any of these let us know by taking a photograph and uploading to iNaturalist. Photographs and identification tips are also available as a downloadable Species to Spot guide (PDF 330KB). 

Montage of six photographs of the Species to Spot, with City Nature Challenge 2021 text overlaid.

Dark-edged bee-fly (Bombylius major

These bee-like flies are commonly seen in springtime, hovering over flowers from which they drink nectar from with their long proboscis (‘tongue’). Unlike bees and butterflies, they cannot retract or roll up their proboscis, so it is always held out front. Other tips for distinguishing them from bees are their large eyes, short antennae and thinner legs. 

Photograph of the Dark-edged bee-fly (Bombylius major) on a flower.
Dark-edged bee-fly © Public Domain

Since 2016 Bee-fly Watch has been recording when and where the dark-edged and other bee-flies emerge. Over time this can provide information on how the species is doing in the UK. We can also see how weather effects the dark-edged bee-fly, for example the warm spring of 2019 meant that they were seen unusually early.  

Find out more about bee-flies in our blog from 2020 or listen to curator of flies Dr Erica McAlister discuss them in the Natural History Museum UK Biodiversity Facebook group

Orange-tip butterfly (Anthocharis cardamines

Around 30 different species of butterflies have been recorded from Greater London, but many are under recorded as butterfly enthusiasts tend to visit nature reserves and the countryside rather than urban parks and gardens. We would love to see photographs of any butterflies you see during City Nature Challenge, but are particularly interested in the orange-tip, which is a spring species overlooked in London. 

Photograph of a male Orange-tip butterfly (Anthocharis cardamines) on a flower.
Male orange-tip butterfly © Quartl CC BY-SA 3.0 via Wikimedia Commons

Orange-tip males are distinctive as their hindwing has a patch of orange, but this is absent in females. However, both sexes have their wing undersides marked in green, unlike other species of white butterfly. Orange-tip butterflies lay a single egg on various mustard species – so watching these plants can be a good way of finding the more cryptic female. Don’t forget to photograph and upload the plant to iNaturalist as well! If you find their orange egg you could visit again a couple of weeks later and try to find the green, slightly fuzzy caterpillar. 

Like the bee-fly, monitoring butterflies can help us find out how their populations are changing with changes in the environment, such as climate or urbanisation. Find out more about butterflies in London and the work being done to create new habitats for them with the Brilliant Butterflies project.

Garlic mustard (Alliaria petiolata

This plant has many other local names, including Jack-by-the-hedge, Jack-in-the-bush and hedge garlic. As its names suggest, it commonly grows in shady areas at the base of hedges and the leaves smell of garlic. Garlic mustard has bright green, hairless, heart shaped leaves and small white flowers in spring. This plant is the one of the food plants of orange-tip butterfly caterpillars, so helping map where it occurs gives scientists an idea where the butterfly could potentially breed.

Photograph of the plant Garlic mustard (Alliaria petiolata) in flower.
Garlic mustard © Robert Flogaus-Faust, CC BY 4.0 via Wikimedia Commons

Garlic mustard is often considered a weed and in urban areas is vulnerable to being strimmed down or treated with weedkiller. This and other pavement plants should instead be encouraged – their leaves are food for the larvae of insects, and their flowers provide for food for pollinators. I would argue that green leafy plants and colourful flowers are more beautiful than dead brown ones too! Some London boroughs have already stopped or reduced the use of weedkillers and tolerate or even encourage wildflowers at the base of trees and verges – if yours has not, consider writing to your council.

If admiring ‘pavement plants’ during City Nature Challenge inspires you to learn more about identifying your local plants the Botanical Society of Britain and Ireland (BSBI) is a great website to explore. 

Grey squirrel (Sciurus carolinensis

Greenspace Information for Greater London (GiGL) collates, stores and shares information about nature in London. Surprisingly there is sometimes more data available for rarer species than common ones! This is because seeing a rare animal is a memorable event which people will make a record of but encounters with common ones tend not to stick in the mind long enough to make a note of them. 

Photograph of a Grey squirrel (Sciurus carolinensis) on a tree with a nut in it's mouth.
Grey squirrel © Public Domain

During City Nature Challenge don’t forget to record the ‘everyday’ species too, including the grey squirrel. The grey squirrel was introduced into the UK in the 1800s and is one of London’s easiest to encounter mammals – often visiting garden bird feeders. If you see one, take a photograph and upload to iNaturalist

If you want to continue recording mammals the rest of the year, try the Mammal Mapper app from the Mammal Society The app is easy to use and includes guides to help you identify the mammal and/or field signs, such as footprints and droppings. You can use the app to record one-off sightings but also those you see during a regular journey, such as a work or shop commute. Records from the same place and during a known period are particularly useful as they allow scientists to estimate populations of mammals, as well as where they live. 

Yellow cellar slug (Limacus flavus

Slugs don’t have a lot of fans, often getting the blame for eating garden plants. I think that’s a shame as only a few of the 40-odd slugs in the UK cause damage to plants. Other species have diets only of earthworms, or fungi, or in this case already dead plants. The yellow cellar slug and it’s relative the green cellar slug (Limacus maculatus) are detritivores – feeding on decaying plant material, helping gardeners and ecosystems by returning nutrients to the soil. 

Photograph of a Yellow cellar slug (Limacus flavus) on a dead log.
Yellow cellar slug © Imogen Cavadino / Royal Horticultural Society

Like many slugs we don’t have much information on where the yellow cellar slug occurs in London, and if it is being replaced by the green cellar slug. Help us out by uploading photographs of cellar slugs or others you see to iNaturalist during City Nature Challenge. Slugs are vulnerable to drying out so are best found after rain or hiding under logs, stones and pots. Looking around your garden with a torch after sunset is a good way to find them too. 

You can help out with garden slug research all year round by taking part in the Royal Horticultural Society Cellar Slug Hunt

Golden Shield Lichen (Xanthoria parietina

Lichens look like crusts or tiny branches, growing on trees, rocks, walls and even pavements! They are complex mixtures of two or more types of fungi, algae and/or cyanobacteria. The algae or cyanobacteria provide the fungus with sugars made from sunlight, and the fungus provides a structure to live in. There are 1,800 different lichens in the UK and they can be difficult to tell apart, but the golden shield lichen is a distinctive and common one. 

Photograph of a Golden Shield Lichen (Xanthoria parietina) on a concrete wall.
Golden shield lichen © Trustees of the Natural History Museum London

One of the reasons lichens are studied by scientists is that they are good indicators of what pollutants are in the air. Some lichens are very sensitive to air pollution and their presence indicates good quality clean air. Measuring changes in lichen species and cover can be used to monitor air pollution and if it is changing. You can find out more about lichens and air pollution in our Anthropocene hub. 

The golden shield lichen can live in areas with high pollution so is common even in cities. It’s particularly frequent on trees and buildings where birds perch and leave behind droppings which act as fertiliser. If you enjoy finding and recording the golden shield lichen the British Lichen Society have lots of resources to help you find out more about other lichen species.

Take the City Nature Challenge!

If you find one of our target species between Friday 29th April and Monday 3rd May (or any others which interest you!) remember to See it, Snap it, Share it on iNaturalist. Look out for the results of the fourth City Nature Challenge: London after the 10th May! 

Logos of organisers: City Nature Challenge is organised by California Academy of Sciences and Natural History Museum Los Angeles County.