The sound of nature

 

 In my continuing efforts to catalogue all the species on my patch, I have splashed out on another piece of surveying equipment. My trail cameras have given me a detailed insight into the mammals using the site — with one obvious exception: bats.

Bats are nocturnal, small and fast, which makes accurate identification difficult. I have seen bats on site and recorded some with my mobile bat detectors, but that depends on me being out in the field every night and staying there long enough to pick up everything. After all, not all bat species fly at the same time of night.

I began by looking at devices sold by Wildlife Acoustics, such as the Song Meter. That got me interested in using sound to identify species. These devices can now help identify bats, small mammals, some insects and birds. Further research led me to the BTO acoustic pipeline, an ambitious programme that analyses sound data and uses machine learning to identify species.

From there, I started exploring the options in earnest, looking at Wildlife Acoustics, Titley and finally Batlogger. After much deliberation over recording types and price, I opted for the Batlogger S2 detector.

The Batlogger S2 is a static logger controlled by an app. The device is small, well-constructed, and easy to use, putting it head and shoulders above the PippyG I had been trying to get to grips with. That said, for the price and with a little perseverance, the PippyG is a good bit of kit — as long as you can understand how to operate it.

The Batlogger app makes setting up the device simple. Strap the unit to a tree with a clear recording area, then activate it using the app. The app works on Android and iOS, connects to the device via Bluetooth, and records its location using the phone’s GPS. You can also schedule when the logger is active. It has an internal SD card, so there is no need to keep swapping cards in and out, and it charges via a lead to your computer, which is also how you download the data.

The data is saved as .wav files, which then need to be analysed. I have used the free version of BatExplorer, but because I am not trained in acoustics or bat identification, I found it difficult to use. It looks like a powerful piece of software, with several ways to present the data, but I needed something a little more approachable.

After experimenting, I opted to use the BTO acoustic pipeline, partly because the analysis is accessible and partly because my data can contribute to wider research, as my bird records on BirdTrack do.

Acoustic analysis is very new to me, but the data produced by the pipeline is clear and approachable. Each automatic identification is given a probability score between 0 and 1. Reading through the literature, the suggested threshold appears to be 0.5, with anything below that disregarded. The statistician in me feels that 0.5 is too low, especially given some of the species suggested in the results. So, for my own analysis, I set two additional thresholds: 0.75 as an amber level, where a species has a good chance of being correct, and 0.9 as a green level, where I felt the identification was acceptable. To help with this, I aggregated the data from the two surveys I ran in June and displayed the results as boxplots. This allowed me to look at the median, mean and interquartile ranges for each record. The final factor I considered was the number of contacts.

So, what species did I find?

After aggregating the data into Chiroptera and other species, for bats at the 0.5 level, 9 species were identified; at the 0.75 level, 8; and at the 0.9 level, 6.

I think it best to use a sensibly high figure as an ID value, so I am only accepting Common Pipistrelle and Soprano Pipistrelle as definitely present on the site, with Brown Long-Eared Bats, Leisler's, and Noctule as possibles. I now plan to review the literature to better understand the ecology of those species at my site. 

The non-bat species, as shown below, offers the most interesting records, but one for which, despite the high probability value, I have the least confidence.

In this analysis, only the Brown Rat fails to reach even the lowest level of acceptance. The other rodent species, like the Wood Mouse and Yellow-necked Mouse, are expected. Wood Mice are widely present on site, and although Yellow-Necked mice have not been identified, they are possible; it's hard to differentiate the two in trail camera footage. 

Harvest Mouse was a very surprising record, and I need to understand their audiology and ecology to determine whether they are likely to be present on the site. There is a section on my patch that is suitable habitat, but it is not in the detector's location.

I know that Bat detectors can detect grasshoppers and crickets, but I would have been sceptical of the presence of two species of Bush-cricket had I not identified a Speckled Bush-cricket nymph only the week before.

Lastly, there are the shrews; they communicate in ultrasound, and so it makes sense they would be detected. Both Common and Pygmy Shrews have been recorded on the site, and Water Shrews are suspected. 

This information gives me some interesting species identifications that warrant closer investigation. I now need to find ways to confirm the presence of Water Shrew and Harvest Mice.

I have only used the logger twice, and I need several more runs and practice with it before I feel more confident. I also really need to understand animal sounds better.

With every new device, my understanding of my patch increases.

An early feast

Today, whilst out birding, something caught my eye. I have started visiting Warwick Racecourse more often this past year, mainly to build up a species list for the site and to get some nice photographs of different birds. 

At this time of year, I am usually focused on the Skylarks and the returning warblers; however, today, what caught my eye first was a flock of Starlings. Starlings are not unusual on site. They are present all year round in small flocks, usually on the short turf by the football ground. Here they potter over the grass, looking for insects and probing for leatherjackets. Today, however, they were further over near the water channel. They sat along the fence line, some of them shooting into the air, hovering and then returning to the fence. If I couldn’t see directly that they were Starlings, I would have identified them as stocky flycatchers, twitching into the air, fluttering and returning to a perch. It was this odd behaviour and that thought of the flycatcher that held the answer. 

Taking a moment to look around me, I noticed that the air was filled with black flies. Flies are often a very overlooked taxon, unless they are flying around your food, but they are incredibly important ecologically. The flies I could see were familiar to me. 

They were jet black, some about an inch long. They floated in the air with their legs dangling, looking like some kind of drone. They seemed to bob on the air currents, settling occasionally on vegetation. These flies are known as St. Mark's Flies (Bibio marci) or the hawthorn fly. They are called St Mark’s flies because their emergence flight period usually coincides with St Mark’s saint day (25th April). 

Image from Warren Photography - https://www.warrenphotographic.co.uk/28027-st-marks-fly-in-flight

The fly is known for its spring appearance. Its larvae live in the soil, feeding on roots and decaying vegetation before pupating into their adult forms, which then take to the air, slowly drifting in swarms with their legs hanging down. This stage is short-lived, lasting perhaps a week as they search out a mate. During this week, they sustain themselves by feeding on the nectar of fruit trees and hawthorn flowers, making them important pollinators for these species. 

In many ways, this display of floating dancing flies is a terrestrial form of that exhibited by Mayflies over our rivers. These swarms form an important food source for many species. The Starlings had identified this and left their usual spot to take advantage of the glut of food.

It's one of nature's miracles, the ability of such tiny organisms to synchronise and emerge together. Sometimes it's the small things that reveal the most.

An upgraded Mostela

 

I have embraced camera trapping as a medium for observing and recording nature. What started as a whimsical addition to my arsenal of ecological tools has turned into a passion. I have been running cameras for over 10 years, have experimented with several techniques, and have even published a book on the topic.

One of the most interesting tools in camera trapping is the Mostela. I have blogged about this device before. Mostelas are designed to improve the detectability of small mustelids such as Stoats and Weasels.

Mostela as detailed by the Vincent Wildlife Trust 2022 (image courtesy of Vincent Wildlife Trust)

They are essentially a box with a drain pipe entrance that contains a camera. They can be baited or unbaited. The theory is that these spaces will be used by small mammals such as voles, mice and shrews; they will visit the site for food if baited or just investigate it. Their continued presence creates a scent trail that Weasels and Stoats will follow when hunting.

Weasel recorded in the current fixed Mostela in 2025

Raw Components

In reality, I have had little success with capturing images of Weasels and Stoats. I am not entirely sure Stoats are resident on the site, in person or on camera. Stoats have only been recorded once since 2015. Weasels, however, are resident, but due to their speed, they are not easily detected on camera. On Otter Cam and the mostelas, they have been recorded once a year, whilst the hedgerow camera recorded them on average twice a year.

The greatest benefit I have found is not in collecting mustelid data but in observing the small mammals. Small mammals can be recorded with standard camera placement, but better identification is achieved with small-mammal rigs and mostelas.

I have used home-built mostelas for over two years, as well as purpose-built ones purchased from the Netherlands (An expensive approach!), and now feel like I want to experiment with the design.

Assembled

One drawback of the mostelas is that, during the daytime, the closed chamber makes it still very dark and often requires infrared to make any visitors visible, making the visitor's pelage colour hard to see. This can be important in identification. To counter this, I am experimenting with a translucent lid that should give better colour clarity during the day.

I have also removed the base plate to reduce costs, provide a more natural view, and allow the camera to be placed more effectively. Often, the best camera positioning involves tilting the camera down. With Gardepro and Bushnell cameras, which are my preferred brands, the lens is often quite high on the device, meaning that individuals moving closer to the camera are often missed or hard to see. Without a base, it is possible to dig a trench for the camera to sit in.

To build this mostela, I have used marineplywood that I bought online pre-cut to size. For the entrance tubing I am experimenting with two entrances opposite to each other using bend fixtures bought from Amazon. This cuts down on the difficulty of cutting and sealing a length of drain pipe.

I have tested the principles in the back garden but this weekend I will install it in the wild to replace my existing mostelas that is slowly disintegrating.

58 and counting

 

Today is day 88 of the year; over the last 88 days, I have seen 58 different bird species.  Just over halfway through this year's attempt to complete the Warwick 100. This is the local attempt for local birdwatchers to see 100 different species over the course of a year. I decided back in January to keep a species list and track the number of species I recorded week by week.

This graph shows the week-by-week increase in species, essentially a Species Richness curve.

The most interesting species seen so far have been:

Northern Shoveler

Mandarin Duck

Gadwall

Oystercatcher

As part of this effort, I spent last weekend scouring Warwick.  On  the Friday, I visited the Chase Lakes, the Hopyards, St Nicholas Park and finally the flash at the Saxon Mill travelling along 5 Km of the River Avon. On Saturday, I visited the Racecourse, and on Sunday, I went to my normal patch. 

In total, over the 4 hours of survey time, I recorded 46 species. This shows how quickly a species list can be built up over a relatively short period. The key is to visit as many different types of habitats as possible. We are lucky in Warwick to have woodland, farmland, grassland, rivers, lakes, and reedbeds.58

Ups and Downs for Raptors

 Birds of prey, as apex predators, are often used as indicators of ecosystem health. Their fortunes reflect changes lower down the food chain and can help us understand how other species are responding to wider environmental pressures.

 I have accumulated enough data over the years to begin exploring these dynamics more meaningfully. So, when I recently found myself musing that I seem to be seeing Peregrines far more often than I used to, I dug a little deeper and put that feeling into context. That thought was really the combination of two separate observations: first, a Peregrine perched on Guy’s Cliffe House, and secondly, how rare it has become for me to see Kestrels at all.

Peregrine

Raptors have had mixed fortunes in the UK, and their numbers have changed drastically within my lifetime. As a child, seeing a Buzzard in Warwickshire was a rarity; now they are ubiquitous, and it is the Red Kite that still feels like a novelty. Kestrels were once abundant; no car journey felt complete without spotting one of these wind-hoverers over the motorway. As for Peregrines, those required a special trip to places like Symonds Yat. Thirty years have passed since my childhood, so what does my local patch tell me about raptors and how they have changed?

After watching the Peregrine perched on the house for a while, I returned home and looked back over the data I’ve collected. I keep a master database spreadsheet that tracks frequency, numbers, and abundance for all bird species recorded. When comparing species, I use a relative abundance measure that weights sightings by the time spent in the field. This helps account for extraneous factors that can otherwise skew results. I plotted these values as a graph and added some contextual information.

 I chose to look at all raptor species that have occurred on my site since 2004. Owls were excluded because my survey methodology substantially underestimates their numbers. When I first started recording, there were three main raptor species: Buzzard, Kestrel, and Sparrowhawk. This has since increased to five, with the addition of Red Kite and Peregrine.

 Buzzards have always been, and continue to be, the most abundant species. They are seen on practically every visit and, pleasingly, in 2024, they nested directly on the patch. Despite low rabbit numbers, their favoured prey, they continue to do well, raising two to three young locally. This mirrors the national picture, where Buzzards are now a stable and widespread species after expanding from their upland strongholds during the 1990s.

Sparrowhawk

 In contrast, Kestrels have undergone a serious decline over the same period and are now Amber-listed. The loss of rough grassland, agricultural intensification, and increased competition are all thought to be contributing factors. Locally, the decline was accelerated by a specific event. A tree in which a pair frequently nested was damaged when a winter storm in 2022 tore off the top of an Ash, exposing the nesting cavity. The loss of that single tree has had a noticeable effect on sightings. With low national numbers and no replacement pair moving in, the area has yet to be recolonised. Despite an abundant vole population in the meadow, I suspect this will remain the case for some time.

 Sparrowhawks are common across the site, as they are around the surrounding housing estates. They remain at a steady but relatively low abundance, which likely reflects their speed and ability to evade detection rather than true scarcity. As specialists adapted to hunting small birds on the wing, they face little competition from other raptors. Short-term peaks in the data likely reflect particularly successful breeding seasons rather than a long-term trend. National Breeding Bird Survey data suggest Sparrowhawk populations are broadly stable following their recovery from pesticide-driven declines in the mid-20th century.

Red Kite

 Pesticides such as DDT had perhaps their greatest impact on Peregrines, which came close to extinction in the 1960s. Their recovery stands as a flagship conservation success. Numbers have risen dramatically, and since the turn of the millennium, they have increasingly colonised urban and suburban sites. A local example is the nesting pair on Leamington Town Hall, which first bred in 2017 and have since raised more than 30 fledglings. My patch lies close enough to this site to be used regularly as a hunting ground, and many of this winter’s sightings appeared to involve an adult teaching a juvenile. Peregrines are territorial, so I don’t expect abundance to increase further — but wouldn’t it be something if they eventually nested in the ruins of Guy’s Cliffe House?

The final species of note is the Red Kite. I saw my first one when studying in Aberystwyth in the late 1990s, when the idea of them occurring in Warwickshire seemed laughable. Now they breed within the county and continue to increase in number. They first appeared locally in the early 2020s and are slowly becoming more regular, with the county still very much in the colonisation phase following reintroductions in Wales and the Chilterns. I hope breeding will occur closer to the site in future, though that will depend on factors such as nest-site availability and competition with Buzzards.

Buzzard and Kestrel

 So, what does all this say about raptors more generally? It’s clear that my small patch broadly mirrors regional and national trends. Generalist species like Buzzards and Red Kites appear better able to exploit our fragmented landscapes and varied food sources. It shows that when persecution pressure is lifted and sufficient nest sites are available, raptors can and do recover. At the same time, it highlights that some specialists continue to struggle. Sparrowhawks, despite their specialisation, seem to benefit from the widespread feeding of garden birds; here, there is nearly always an all-you-can-eat buffet somewhere nearby. Kestrels, by contrast, remain heavily reliant on rough grassland and vole populations, much as Buzzards once depended on rabbits.

My local story also illustrates how the loss of a single tree can significantly affect species abundance. In this case, the cause was weather rather than environmental vandalism, but it underlines how vulnerable populations can become once numbers fall. The takeaway is this: national recoveries are real but uneven; declines can be rapid and locally catastrophic; conservation often hinges on surprisingly small pieces of habitat; and patch-based recording matters. It really is the canary in the coal mine, and it contributes to the bigger picture.

When data can reveal a human truth

 

There are times when I review my data simply for pleasure. Not everyone would call that fun, but for me, there’s real satisfaction in looking back at the wildlife numbers I’ve gathered on my patch since I first began tracking them.

Whenever I revisit the dataset, my attention is immediately drawn to the gaps. Little voids that tease my more obsessive tendencies and make me wonder what stories were lost. The biggest gap was in 2018, when I collected no data for three months. A fallen tree trunk had crashed into the stanchion of the old stone bridge, forcing its closure for repairs. During that time, I couldn’t reach my patch. It felt strange and, frankly, unsettling to lose my weekly visits. Smaller gaps over the years come down to bad weather or illness, but the two-month gap in 2011 belongs to a darker chapter, a resurgence of my anxiety to a state where my focus was entirely on ensuring I could make it to work each day.

Table showing the average recording survey time on my patch

An important part of who I am, something I no longer hesitate to share, is that I have Generalised Anxiety Disorder. Thankfully, mental health no longer carries the stigma it once did, and I make sure the students I work with understand that these struggles can happen to anyone, and that a fulfilling life is still entirely possible. I won’t go into the details of what lies beneath my anxiety; therapy and introspection have given me clarity, but those details are for me alone. What matters is that I’ve come to accept that my anxiety is part of who I am. It doesn’t define me, but it has shaped my personality and my life in irreversible ways.

I had my first recognisable anxiety attack at 16, and a small breakdown in the final year of university. Strangely, my patch became part of my recovery. At its worst, my anxiety manifested as an odd mix of agoraphobia and claustrophobia, seemingly contradictory, yet somehow, I managed both at once. Sometimes they alternated; sometimes they arrived together, leaving me avoiding being indoors but unable to stray too far from home.

My visits to the patch began in 2002 as a way to keep my ecological skills sharp and to coax myself out of the house. I started simply walking around and taking in the air, but the scientist in me soon began making notes, casual observations at first, without a strict method. In 2004, as my love for the patch deepened, I established a clear protocol and began recording every species I encountered. By the end of 2025, I had visited the site 982 times, spending a total of 797.7 hours there, the equivalent of 33 full days immersed in nature.

Nature has always been a powerful healer for me and can be for many others. Time outside is actually prescribed now by doctors to treat stress and depression. Just 30 minutes in nature can lower cortisol levels, lift mood, and boost immunity.  My patch has carried me through sad and difficult times, and it helped me hold on to my sanity during COVID. I’ve grown enormously as an ecologist, coming to know so many species with an almost intimate familiarity. And yet, those gaps still catch my eye. I regret not being just a little stronger, not managing even a couple of visits during those hard moments. But the truth is: those gaps tell my story just as much as the data tells the stories of the birds and animals I record.

From Blue Tits to Great Tits: Rethinking bias in conservation

 It’s interesting how we often attribute distinct personalities to different bird species, drawing on stereotypes shaped by their appearance and behaviour. These impressions are rarely about individual birds, but rather about the collective image we form of a species. For example, Blue Tits and Great Tits are two of the most common birds I encounter, both frequent visitors to gardens and parks. Yet I realise I view these species through the lens of stereotypes, sometimes unfairly.

Stereotypes about birds are deeply ingrained in our culture, think of the elegance of swans, the wisdom of owls, or the ill fortune associated with magpies. In my own experience, I’ve always seen Blue Tits in a positive light, perceiving them as friendly and cheerful. Their small size and vibrant plumage give them an approachable air, and their chirruping calls seem engaging and pleasant. At the bird table, they flit about energetically, often appearing non-confrontational, and are often bullied by larger birds, especially their bigger relative, the Great Tit.

Great Tits, on the other hand, strike me as more assertive. Their stocky build and bold black markings remind me of a mask, almost like a burglar’s disguise. This impression is reinforced by their ability to mimic the calls of other species and their tendency to dominate at the bird table. I sometimes think of them as boastful, puffing out their chests and showing off their striking uniforms, perhaps the very model of a modern major general. Words like pride and conceit come to mind when I observe their behaviour.

However, I recognise that these descriptions reflect my own biases. The reality is more complex: Blue Tits can be aggressive towards smaller species such as Long-tailed Tits and Coal Tits, while Great Tits themselves may be bullied by Robins. Watch Great Tits for long enough, however, and you will find them as endearing as Blue Tits. They share many traits but fill very different niches. They are less flighty and more confident in their actions. Unlike Blue Tits, they will feed openly on the ground and will take to prominent treetops to sing. Thinking about Great Tits now, I realise they often herald the approach of my favourite season, spring. Their calls change subtly and become more strident.

Reflecting on these tendencies, I’m reminded of the importance of questioning our assumptions—not just about birds, but about all living things. By acknowledging our biases, we can strive for a more nuanced and accurate understanding of the natural world. It has long been a problem in nature conservation that it's far easier to raise money to save a species of cuddly animal like a bear or rodent than it is for a species of spider or snake. Some of our revulsion for certain species is biologically ingrained; we have an aversion to species less like us, bilateral species, those with radically different body shapes. The BBC ran an article on this back in 2012 and Green Earth explored it in 2024

Both articles describe the innate human bias that affects our efforts to defend biodiversity. This aligns with my growing sense that nature conservation should focus primarily on habitat protection and creation. We need to ensure ecosystems are stable and functioning and allow nature to take the lead. Species recovery will follow. I recall several Dormouse reintroductions in the early 2000s that failed because too much effort was placed on releasing individuals and boosting the local population before the habitat was repaired enough to support them. Of course, habitat protection is part of species reintroduction, and the lion's share of funding comes from species conservation, but we need to find an effective way to protect all species, regardless of their appearance or our own perceptions.