Compensating for Photography Bias in Pollinator Studies

Recently I’ve been concentrating a lot of my iNat observation efforts on photographing pollinators in context but I’ve noticed an unintended bias in my observations. Far too many of my observations are of pollinators on introduced plant species. It seems to me that this bias is at least in part due to the fact that it is easier to photograph a pollinator on a large showy plant where the insect may spend more time than they might on a smaller native plant. For example I have lots of shots of bees on common garden chives but very few on salal (Gaultheria shallon) a far more common plant here that I know is very popular with Bombus species. The problem in this case is that the salal blooms are small and the bee may only visit for seconds before moving on making photography very difficult. In other cases eg. Big leaf maple the blooms a just too high up to be able to photograph the species that are on the flowers.

How does one compensate for this bias? Does anyone have any tricks of the trade?

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Why do you want to compensate? Is there a particular research question that you’re collecting data for?

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As an example if I wanted to determine what plants are most preferred by a Bombus species how I would I compensate for the fact that it is far easier photograph the bee on a large flat flower than small urn shaped flower and therefore there will be more photos of bees on the former even if the bees prefer the latter.

In some cases it won’t matter. Today I was at a small patch of flowers and all of the Bombus were on Comfrey, a terrible plant from a photography standpoint. The clovers and chives were being visited by other species. When the maples in my yard were in bloom, the Bombus weren’t really active yet, so the only things that I photographed on it were Andrena.

But if you’re trying to determine if one plant is more popular than another, the only thing I can think of would be to just spend the same amount of time at each and see which one really has more. A point to remember though, Bombus have no standards at all when it comes to what flowers they want. Some of my best sites are fields filled with crappy non-native/invasives with minimal natives to work with but I’ll have all ten local species including Bombus affinis and pensylvanicus. Big showy flowers aren’t just more noticeable to us, they are also more noticeable to a generalist pollinator like Bombus, so one part of the reason that you’re shooting more of them on non-natives might be because the Bees are easier to shoot on those flowers, but a large part of it is also simply, that’s where the bees are.

I work for a couple of conservation groups and a mindset that I run into a lot is the assumption (hope?) that Bombus prefer conservative native flowers, mainly because it’s easier to get funding from big showy Bombus. Unfortunately that’s not the case, Bombus will take anything that’s somewhat flower shaped. If you want something that does prefer natives, I would recommend looking to some of the floral and edaphic specialists.

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If you’re trying to document what you’re seeing through iNat, how about making medialess observations of the instances you see insects on flowers but didn’t take a photo? Or you could keep tally on your own in another format like in a spreadsheet or notebook.

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iNat isn’t a great platform for answering questions that need presence/absence data, because it only collects presence data. These biases are just part of the platform, and need to be taken into account by anyone that uses the data for any purpose. For example I mostly take photos of species that a) interest me, b) I don’t know what they are and c) are probably identifiable. So that means I take lots of photos of bombus, few photos of honey bees and fewer and fewer photos of species that I’ve already learned to ID. Of the 3000 bee observations I have in iNat only 40 are Apis mellifera, despite them being bar far the most common species I see. By some quirk of fate I’m responsible for 49% of all Calliopsis rhodophila observations, which would definitely bias any study you tried to do of their habits via iNat observations.

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I’m responsible for more than 50% of subgenus Macroteropsis. It’s not like they are rare or hard to find, I just enjoy observing small bees…

Apis is not always the most common bee in my neighborhood (probably not many hives in suburbia). Depending on the time of year, Dialictus (unknown species), Halictus tripartitus, Bombus pensylvanicus, or Lithurgopsis apicalis.

My bias is camera skill, so even though I try to be comprehensive, very small or very fast pollinators are underrepresented. I also don’t see the point in uploading every individual I see of each species each day (or week), but I try to make notes on abundance and behavior. Time is an issue too - do I want to spend 10 minutes on my belly trying to photograph Perdita on Euphorbia (sandmats)? What else is going to fly by while I’m watching a syrphid on a sunflower? I know I miss many large butterflies and micro moths.

Something worth mentioning is that conventional pollinator studies also have biases, with debates about bowl and vane traps, netting, and other observation methods. Usually, you find what you’re looking for!

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If you want to study a species, it’d be easier to follow specimens around than collect data from a planted flower, actually if it’s easy to study those flowers, it could be a study of its own about polllinators visiting introduced taxa.

I think instead of photographing you could just record a video and then either post a frame from it as an observation, or post a GIF (yes that’s actually possible to do). That works if the bee or another pollinator insect visits only for a few seconds and getting a clear static photo is hard

In that case, there probably wouldn’t be a need to include a photograph of every time you see a bee on a particular plant here on iNat (and it sounds like it’s preventing you from conducting a well-designed study–and you and your camera could also be influencing their behaviors). What you need to do is keep a tally sheet of how many visits bees make to one species compared to the other. As examples, here are two approaches in the published literature:

  • “Every hour between 08:00 and 22:00 hr, each clone was observed for 5-min at each pair of male and female clones to count pollinator visits by Andrena species. Hourly counts of andrenids foraging on willow flower catkins were made on three consecutive dates during the peak flowering period in 2015.”
  • “On 18 separate days over the course of 5 wk, we continuously [from 0930 to 1315 Daylight Saving Time (DST)] recorded the frequency (visits per minute) with which bumble bee foragers collected pollen from each plant species”

If you’re interested in digging deeper in the literature, here’s Google Scholar results.

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