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The Wild Honey Bees the Trees and the Woodpeckers

This work is licensed under CC BY-NC-SA 4.0

Call to Naturalists

If you know wild bee colonies, if you like to observe nature and would like to take part in our Citizen Science project in Luxembourg, Europe, we invite you to contact us:


Honey bees in the wild that survive

in today's environment are particularly important. In this article, we present the two components of our citizen science project: monitoring demographic of bee colonies, on the one hand, and monitoring the occupation of woodpecker cavities by bees, on the other hand.

The Demographic Study of Wild Bee Colonies

The first part of the citizen science project of the "Honey Bee Wild" network is to determine the lifespan of bee colonies living in the wild in Luxembourg. This investigation is based on a protocol developed by Vincent Albouy (OPIE Poitou-Charentes) founded on the pioneering study by Thomas D. Seeley in the 1970s in the Arnot Forest near Ithaca, New York (Seeley, 2019).

The OPIE protocol has enriched the Seeley protocol in two ways: a more detailed description of the nesting sites and the inclusion of other cavity dwellers in the observation.

The approach recommended for naturalists is easy to implement. This involves observing the bee colonies four times a year. The main criterion is the presence of bees, and especially bees that have collected pollen. We look at all bee colonies living in the wild to determine their average lifespan, regardless of the cavity in which they live: a woodpecker cavity, a natural tree cavity, a hollow wall ...

The worldwide interest in the wild honeybees can be seen at An international study was proposed in May 2020 looking at all wild bee colonies regardless of nesting site in order to determine their average lifespan (Seeley, 2020).

The bee colonies living in the forests in the wild are currently being studied primarily by researchers in Germany (Kohl and Rutschmann, 2018) (Mittl, bibliographical overview, 2019). In 2020, photographer Ingo Arndt and Professor Jürgen Tautz published the book "Honey Bees - Mysterious Forest Residents". In France, the occupation of the woodpecker cavities by honeybees and other cave dwellers was observed in the course of long-term studies in the Orient Forest (Fauvel, 2014), and the invasion of swarms of bees into gray woodpecker cavities during the breeding season in the state forest of Loches in Touraine (Dubois, 2018) .

About 80% of swarms of bees living in the wild do not survive the first winter (Seeley, 2017). The rigor of natural selection helps maintain properties useful for survival (Cooper, 1986). In forest areas, the number of sufficiently large and well-isolated woodpecker holes or natural cavities that can house bees' nests is a limiting factor (Ruttner, 1988).

Investigation of the Occupation of Woodpecker Holes by Bees

It is the joy of observing nature and taking walks in the forest that has led us to complement our Citizen Science project with the study of the occupation of woodpecker holes by bees, in partnership with the Luxembourg Central Bird Sanctuary (COL) and in consultation with the forest department of the nature and forest authority (ANF) in Luxembourg.

Bees-occupied great spotted woodpecker cavity in an oak tree in the state forest of Loches in Touraine, France (Photo Michael Dubois)

Our Citizen Science project concerns the nest cavities of black, great spotted, gray and green woodpeckers¹, on the one hand to determine the proportion of woodpecker nests occupied by bees and on the other hand to check whether swarms of bees move into gray woodpecker burrows while young woodpeckers are still in the nest, as this species of woodpecker is on the decline in some regions (De Broyer, 2017). It is possible that the number of bee-occupied burrows in great spotted woodpeckers is much larger than in other species of woodpecker, as they drill a new burrow every year, while the black woodpecker tends to reuse its burrow. Many great spotted woodpecker burrows are occupied by swarms of bees, especially in sessile oak stands that are in the regeneration phase (partial cutting before final cutting). This is a phase in which the stand is very light (50 to 70 trees / ha). (Dubois, 2020).

The monitoring of the woodpecker cavities filled with honey bees or natural tree cavities, which were either reported by the ornithologists of the COL bird sanctuary or discovered during forest exploration, is carried out by volunteers from the "Honey Bee Wild" network. The habitat trees identified by the nature and forest authorities will soon be published on Geoportal. These trees are not necessarily trees with cavities.

This woodpecker cavity from the Merscherwald was occupied by bees when it was felled. a bird's nest is visible in the lower area of the cavity. The large holes in the wall were drilled by wood ants.

The dimensions of the entrance hole indicate that this is a black woodpecker cave. The cavity has probably not been used by black woodpeckers for a long time, otherwise the entrance hole would be blocked and not so round. (Luis Sikora, personal communication).

(Photos Christian Zewen)

The dark color of the honeycomb with the light edge indicates that it is an

early swarm of the year (Albouy, pers. Commun.)

Tree Cavities

Cavities mainly develop in older trees. Ageing and dead trees are essential for cavity dwellers, and the creation of a mosaic of ageing and young populations to replace them promotes biodiversity (Brechtel, 1992). Laurent Larrieu, the developer of the Index of Potential Biodiversity (IBP), has found numerous relationships between the properties of large woods with cavities, bark detachment etc., and populations of insects and forest vertebrates (Larrieu, 2020).

The frequent pruning of pollard trees and trees along road sides leads to injuries causing fungus to rot the inside of the trunk, which then quickly creates cavities. The Pollarded trees are of great interest because it is home to numerous species and its functions are diverse: It is the “Swiss Army Knife” of agroforestry (Mansion, 2019). Hedge landscapes with numerous pollarded trees form a semi-natural habitat in which wild bee colonies often colonize the hollow trees. In some forest areas, pollarded trees were used to demarcate fields. Road side trees are also useful for wild bee colonies, as a Polish study on Linden found (Albouy, personal communication).

This pollard tree, unfortunately cut down, housed a bees nest in the

Cher valley of the Loir-et-Cher region. (Photo Dominique Mansion)

Definitions used in this study

What is a colony of bees living in the wild? We follow the differentiation between wild and managed populations of Apis mellifera, employed in the article “The Conservation of Native Honey Bees is Crucial” (Requier et al., 2019). In the scientific literature, the “wild” state is in contrast to the “managed” state. There is no connection with the indigenous or "autochthonous" ancestry ("native") in contrast to the exotic origin. Attention should be paid to the dual nature of the definitions. Other distinctions are possible (Mittl, 2017) (Wermelinger, 2020).

Honey bees in the wild - wherever they live, whether in a woodpecker or natural cavities or in a hollow wall - have, by definition, chosen their own nesting site and receive no immediate help (treatments, feeding ...) nor exploitation (honey extraction...) directly by humans. Most of the bee colonies living in the wild are unlikely to be indigenous. There is a continual interaction between beekeeping selection for the purpose of maximum honey yield at the expense of intensive care and the natural selection, which adapts the mixed-breed strains to the local conditions (Albouy, 2020).

“Locally adapted bees” has been understood to mean mixed-breed bees living in the wild for several years, exposed to natural selection and able to survive in the habitat that they have spontaneously chosen without human interference. These locally adapted strains resulting from natural selection can only occur permanently in areas in which the density of the bee colonies is low and the effects of beekeeping are insignificant (Albouy, pers. Mitt., 2020) (Shaw, 2015). The local imprinting takes place where the fertilization takes place, that is, in areas of drone congregation. It does not depend on the size of the area but on the topography. For example, an area can be extremely isolated because of the surrounding wooded and agricultural land. In the United Kingdom, different strains of the Apis mellifera mellifera, known as the "dark bee", have evolved less than 30 km from one another. The locally adapted dark bee is probably no longer available in Luxembourg.

The subspecies Apis mellifera mellifera is native to much of western and northern Europe and relic populations are still present in some remote regions, e.g. Ireland and Scotland. Conservation efforts should not be limited to the 100% pure Apis mellifera mellifera. Populations that are 90% pure are also very worthy of protection and this is a criterion for setting up protected areas (Requier, aforementioned article, 2019). There are areas of natural overlap of lineages (or subspecies) e.g. Italy, Spain and Eastern Europe (Requier, box 1 of the same article, 2019) (Ruttner et al., 1990) (Cooper, 1986).

"What is more important is the new wild; those bees that survive in today's environment. What you need is a reduction in the movement of bees and local sourcing ”. (Jonathan Powell, personal communication). In Ireland, the North County Dublin region has introduced a mentoring system for budding beekeepers (McMullan, 2018).

Know and protect

"You can only protect what you know." One promising way is to study colonies of bees in hollow trees under living conditions that are as natural as possible, that is, in the forest or in tree-rich areas, in order to collect objective data that may make it possible to implement protective measures for locally adapted bee colonies living in the wild, their preservation is of crucial importance as it strengthens the bees' resilience.

With thanks

This contribution is the result of an intensive exchange of information and experiences, especially with Vincent Albouy, Sigrun Mittl, Michael Dubois, Fabrice Requier and Liliane Burton.

The Honey Bee Wild team

1. The green woodpecker is present in many habitats and belongs to the common woodpecker species. Its caves can be used by bees but are not easy to recognize in the forest, as the green woodpecker has no special requirements with regard to the cave trees, unlike other species. The medium-sized woodpecker and the small woodpecker are not included in the study, as both species create their burrows in dead wood, which is initially quite dry but gradually begins to rot because of the moisture that penetrates the burrow.

2. Further possible characteristics of a habitat tree are, for example: fungal infestation, loose tree bark, broken branches, birds of prey's nest, etc. Four habitat trees are marked per hectare in the public forest and eight habitat trees in Natura 2000 areas.

Further Information

ALBOUY, Vincent (2019) : Abeilles mellifères à l’état sauvage – Une histoire naturelle, éditions Terran

ALBOUY, Vincent (2020): Les abeilles mellifères à l’état sauvage dans le nord de la Nouvelle Aquitaine. Conférence apicole internationale du 21 novembre 2020 « Abeilles sans frontières »

ARNDT, Ingo et Jürgen TAUTZ (2020): Honigbienen – Geheimnisvolle Waldbewohner. Knesebeck-Verlag

BRECHTEL, Fritz (1992): Alt- und Totholz – voller Leben. Naturschutz bei uns. Landesamt für Umweltschutz und Gewerbeaufsicht, Rheinland-Pfalz.

COOPER, Beowulf (1986): The Honeybees of the British Isles, edited by Philip Denwood, British Isles Bee Breeders’ Association.

DE BROYER, Alain (2017) : Le Pic cendré Picus canus, un nicheur en voie de disparition en Belgique. Analyse de la tendance pour la période 2008-2017. Aves 54/4

DUBOIS, Michael (2016) : Picidés – Forêt domaniale de Loches

DUBOIS Michael (2018) : Pic cendré I

DUBOIS, Michael (2018) : Pic cendré II

FAUVEL, Bruno (2014) : Le Pic noir Dryocopus martius en Forêt d’Orient (Aube) : 6 années de suivis d’une population nicheuse.

KOHL Patrick Laurenz et RUTSCHMANN, Benjamin (2018). The neglected bee trees : European beech forests as a home for feral honey bee colonies. PeerJ 6:e4602

LA HULOTTE Pic noir n°82 (1-43) et n°83 (1-35)

LARRIEU, Laurent (2020): Les cavités dans les arbres : Des îlots de ressources éphémères indispensables à de nombreuses espèces peuplant la forêt. Conférence apicole internationale du 21 novembre 2020 «Abeilles sans frontières»

Lien vers la partie opérationnelle de ses recherches : que les actes du Colloque international francophone « Bois mort et à cavités - Une clef pour des forêts vivantes » (Chambéry, 2004), parus chez Lavoisier (Tec & doc), 2006 : D. Vallauri, J. André, B. Dodelin, R. Eynard-Machet & D. Rambaud Coordonnateurs. 405 p.

MANSION, Dominique (2019): Les trognes – L’arbre paysan aux milles usages. Editions Ouest-France. Les trognes, essence par essence : Trognes, les arbres aux mille visages Lebensraum Kopfbaum

Mc MULLAN, John (2018): «Adaptation in Honey Bee (Apis mellifera) Colonies Exhibiting Tolerance to Varroa destructor in Ireland.

MITTL, Sigrun (2017) : Apis mellifera und das Bundesnaturschutzgesetz (BNatSchG) der BRD – Ist die Art Apis mellifera (Westliche Honigbiene) ein Wildtier und welche Folgen hätte das für Gesetzgebung und Artenschutz ? Oktober 2017, 2. überarbeitete Fassung

MITTL Sigrun (2019) : Ein bisher kaum beachteter Mosaikstein im Ökosystem Wald: Die wild lebende Honigbiene Apis mellifera und die Rolle von Spechten und Pilzen für ihr Überleben

REQUIER, Fabrice et al. (2019): The Conservation of Native Honey Bees is Crucial

REQUIER, Fabrice (2020): Connaissances sur les populations sauvages d’abeilles mellifères en Europe. Conférence apicole internationale du 21 novembre 2020 « Abeilles sans frontières »

RUTTNER, Friedrich (1988): Biogeography and taxonomy of honeybees. Springer-Verlag. RUTTNER, Friedrich, MILNER, Eric et DEWS, John (1990): “The Dark European Honey Bee”, BIBBA, 52 p., traduit en français : Abeille noire Apis mellifera mellifera Linnaeus.

SEELEY, Thomas D. (2017): “Life-history traits of wild honey bee colonies living in forests around Ithaca, NY, USA"

SEELEY, Thomas D. (2019): Lives of Bees: The Untold Story of the Honey Bee in the Wild. Princeton Univ.Press

SEELEY, Thomas D. (2020): « A citizen science study of wild colonies of honey bees ». Natural Bee Husbandry - The international Journal for Bee-Centred Beekeeping – N° 15

SHAW, Wally (2015): What do we mean by locally adapted bees ?

WERMELINGER, André (2020): “Honigbienen – Wildtier oder Nutztier ?” , FREETHEBEES Bulletin – Nr. 17, Dezember 2020.


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