Welcome to Insectcount.dk

This web site presents a project, in which persons interested in nature can make a difference. We will determine the causes of the dramatic fall in the abundance of insects since 1990 and relate this decline to the abundance of insectivorous birds. This document is an updated version that also functions as a reminder for those who might have forgotten. There has been 5000 visits to the web site and data on more than 150 transects have been reported.

About the project

The number of insects has decreased by more than 70% i large nature reserves in Germany, but also in farmland in Denmark during just 27 years. These declines in the number of insects can be measured from the number of insects on the windscreen of cars. The objective of this study is to use citizen science to (1) determine whether the number of insectivorous birds decreases with a decreasing number of insects on the windscreen of cars, and (2) determine the main factors that explain variation in the abundance of insects.


If you are in doubt, send an email to mail@insectcount.dk

Data collection

Insect counts will be based on the number of insects killed against the windscreen, and the number of house martins, barn swallows and swifts on the same route. This simple measure of the number of insects and the number of insectivorous barn swallows, house martins and swifts should be entered in an xls file (see below) (download calcsheet).

Please return the completed data sheet to mail@insectcount.dk

The speed of the car should be the approximate speed on the route. If the distance is 5 km, and if the speed is 60 km/h most of the route, then you should enter 60 km/h.

If coordinates are unavailable, leave the space empty

Wind should be scored as Beaufort from 0 to 12

Cloud cover should be in units of 1/8 from 0/8, which is a clear sky to overcast, which is 8/8

When having driven a certain distance and after having stopped the car, count the number of insects on the window. Clean the window thoroughly before starting a new insect census.  Only data for May-August will be relevant.

Assessing insect abundance with a car

The objectives of this study are to (1) determine whether the abundance of aerial insectivorous birds increases with the abundance of insects on car windows, and (2) determine the main factors that explain variation in insect abundance.

The following publications describe this method, and some of the results can be downloaded from this web site:

Insects are killed after collision with windscreens (car windows) leaving a spot on the window. The abundance of insects killed on windows varies from none or few on cold days and in intensively cultivated farmland to many on warm and sunny days in natural habitats. This measure of insect abundance is highly repeatable on different days and at different times of the day. Insect abundance estimated with a car is also strongly positively associated with insect captures with a sweep-net, sticky insect plates and feeding rates of barn swallows at their nests. Previous use of this method on two transects has revealed reductions in the abundance of flying insects by more than 70% in Northern Denmark during 1996-2017. A German study in nature reserves since the 1970’s also showed a reduction in abundance by 70%. Such large reductions in insect abundance suggest that insectivorous birds will suffer from food deficit, but also that reduction in the abundance of pollinating insects like bees, bumblebees and butterflies will reduce seed and fruit production. Many insects also kill other insects and hence play an important role in controlling the abundance of pests and for ecosystem functioning.


The abundance and the diversity of insects in Europe have declined considerably during recent decades. These reductions have been attributed to farming practice, land-use and associated factors, although significant heterogeneity still requires more research. We used the abundance of insects killed against windshields of car during 1462 transects for a distance of ca. 35,000 km as estimates of insect abundance. The main determinants of insect abundance were features of cars (such as driving speed and car brand), climate (temperature, cloud cover and wind speed), time during the season and the day, ionizing radiation at Chernobyl and at uncontaminated control sites, differences among continents, and amount of fertilizer. These findings imply that a number of abiotic and biotic factors account for spatial and temporal heterogeneity in abundance of flying insects, and hence these factors are likely to contribute to the decline in the abundance of insects.


The following publications describing this method and some of the results can be downloaded from this web site:

The Guardian:
Car ‘splatometer’ tests reveal huge decline in number of insects
Proof of insect apocalypse grows as studies show ‘catastrophic’ 80% decline

Møller, A. P. 2019 Quantifying rapidly declining abundance of insects in Europe using a paired experimental design Ecol. Evol.

Møller, A. P. 2019. Parallel declines in abundance of insects and insectivorous birds in Denmark over 22 years. Ecol. Evol. (in press).

Møller, A. P., Czeszczewik, D., Flensted Jensen, E., Erritzøe, J., Laursen, K., Liang, W. & Walankiewicz, W. Determinants of insect abundance across two continents. Sci. Rep. (submitted manuscript).

Hallmann, C.A., Sorg, M., Jongejans, E., Siepel, H., Hofland, N., Schwan, H., Stenmans, W., Müller, A., Sumser, H., Hörren, T., Goulson, D. and de Kroon, H. (2017). More than 75 percent decline over 27 years in total flying insect biomass in protected areasPLoS One, 12 (10), e0185809.

Møller, A. P. 2013. Long-term trends in wind speed, insect abundance and ecology of an insectivorous bird. Ecosphere 4(1), article 6.

Møller, A. P. 2018. Long-term reductions in abundance of insects in Danish farmland and effects on insectivorous birds. Scientific Reports (submitted manuscript).