When should Tengmalm’s owls eat?

This is a video about a Tengmalm’s owl.

From the British Ornithological Union:

When should you eat?

Which is better for the reproductive success of Tengmalm’s Owls: an occasional feast or a steady availability of crumbs?

Markéta Zárybnická
Faculty of Environmental Sciences
Czech University of Life Sciences Prague
Czech Republic

2 March 2015

One could expect that the reproductive success of birds with large geographical distribution will be higher in the core of their breeding range than on its margin. Here we ask, how a nocturnal avian predator with wide Holarctic distribution – Tengmalm’s Owls Aegolius funereus – deals with contrasting ecological conditions of Northern (core of range) and Central (margin of range) Europe.

On a species level, populations occurring in different parts of the distribution range often face contrasting ecological conditions; these local conditions can modify the selective pressures affecting life-history characteristics, which in turn may lead to variation in reproductive strategies (Tieleman 2009). For example, Dark-eyed Juncos Junco hyemalis, which breed in North America across an extensive altitudinal gradient (Bears et al. 2009), provide a textbook example of within-species variation in life histories. Juncos inhabiting high elevations start to breed later and their reproductive season is constricted so that on average they are able to raise only half the number of young compared to conspecifics living at lower elevations. Lower reproductive success of the montane population is, however, balanced by higher between-year survival rates (Bears et al. 2009). Unfortunately comprehensive studies are scanty and our understanding of the variation in reproductive strategies among populations to maintain their viability is still far from satisfactory.

Birds of prey provide an especially suitable model for intraspecific comparisons as they tend to have large geographical ranges covering areas with contrasting ecological conditions, and show great variability in reproductive effort both within and between populations of the same species (Korpimäki & Hakkarainen 1991, Laaksonen et al. 2002). Moreover, they are well-explored example of huge intraspecific variation in life-history traits, as they are able to adjust their reproductive strategies across space and time according to actual food availability (Hakkarainen et al. 2003, Valkama & Korpimäki 1999). Furthermore, estimating the spatial and temporal availability of main foods of avian predators is relatively easy, making it possible to examine one of the main determinants of reproductive effort in birds (Martin 1987).

Variation in food abundance in both northern and temperate areas has a crucial impact on the reproductive strategies of avian predators, whereby seasons with high food availability lead to increases in clutch size (e.g. Lehikoinen et al. 2011) as well as current and lifetime reproductive success (e.g. Korpimäki 1992). However, at higher latitudes, voles, which comprise the dominant prey of most birds of prey, undergo regular 3-4 year cycles and great multi-annual and intra-seasonal changes of abundance (Korpimäki et al. 2005), while vole abundances tend to be relatively stable both within and between years, showing only moderate seasonal changes with low densities in the spring and higher densities in the autumn (Hanski et al. 1991). In addition, in temperate areas the diet of raptors and owls is additionally enriched with other species such as Apodemus mice (Zárybnická et al. 2013). However, studies comparing numerical and reproductive responses between geographically separated populations that also experience different prey dynamics have not been available so far.

Our primary intention was to compare the breeding density and performance of Tengmalm’s Owls in two geographically distant populations: a boreal population (in Finland) in the core area of the species’ breeding range and a temperate population (in the Czech Republic) at the southern limit of the breeding distribution range in the Western Palearctic. These study areas lie 1500 km from one another and differ substantially in prey availability: densities of main prey (voles and mice) at the temperate study site were consistently lower and more stable than prey populations at the boreal site where vole densities undergo both large inter-annual 3-year cyclic fluctuations and intra-seasonal changes in densities (Fig. 1). These differences in prey availability were closely related to variation in the breeding performance of the respective populations of Tengmalm’s Owls. In particular, owl breeding density showed greater inter-annual fluctuations in Finland where the number of breeding pairs positively correlated with main prey densities while no such relationship was observed at the Czech site. Clutch size was larger in Finland compared to the Czech site and positively correlated with main prey densities in both areas (Fig. 2).

See also here.

Blackbird, song thrush, great tit, dunnock singing

This is a video about a song thrush‘s singing and nest, recorded in Kroměříž in the Czech republic.

Outside my window, early this morning, a blackbird sang again.

A bit later, a song thrush sang.

Still later came a great tit.

Finally, a dunnock‘s song.

What southern European spiders eat

This video says about itself:

Arachnid Anatomy (Orb-weaving spider)

23 November 2012

A new spin on the usual anatomy video: field biology! Basic external anatomy of an orb-weaving spider, using a live, wild specimen. This is a Cat-faced Spider (Araneus gemmoides), a common species found near/on buildings in North America. I’ve used this as a model although typically the Garden Spider (Argiope sp.) is used in zoology labs.

Also: I let a giant spider walk on my hand. Ha! But it’s OK, they don’t bite.

This video was produced by C. Ernst, a Teaching Assistant.

From Wildlife Extra:

Southern European Spiders prefer a Harvester meal (Harvester Ant, that is)

The southern European spider, Euryopis episinoides, has a distinct preference for Harvester ants, researchers have discovered, and identify them without the benefit of guidance from their parents.

The young spiderlings innately have a nose for these ants, report Stano Pekár and Manuel Cárdenas of the Masaryk University in the Czech Republic in an article in Springer’s journal The Science of Nature – Naturwissenschaften.

Euryopis episinoides is a tiny, 3mm long spider that only catches ants – in particular members of the Messor group of which there are more than 100 species.

The female conveniently lays her egg sacks close to such ant nests but this is about as much parental care as she gives to her offspring.

Once hatched, the spiderlings fend for themselves and this includes recognising and catching prey, all on their own.

The Czech researchers wanted to find out if the Euryopis episinoides spiderlings’ hunting activities were driven by convenience or truly by an innate preference for Harvester Ants.

They tested how newly hatched spiderlings that had not yet gone on the hunt reacted to the chemical cues left by three types of prey: Harvester Ants, fruit flies and Nylander Ants.

In just under half the instances, the inexperienced spiderlings assumed a hunting position in front of a paper strip carrying the smell of Harvester Ants – even though they had never before had the slightest whiff of this type of ant.

The researchers also tested the reaction of more experienced spiderlings that had been raised on only one type of prey: again either Harvester Ants, fruit flies or Nylander Ants.

They found that food imprinting changed the spiderlings’ innate food preference. This was because the spiderlings more often than not chose the type of prey on which they were raised rather than Harvester Ants.

In another twist, the spiders used in the experiment fared better healthwise when they ate ants rather than fruit flies.

“Our findings suggest that prey preference is genetically based but also affected by the experience with the first meal,” says Pekár. “Such an innate preference enables Euryopis episinoides spiderlings to rapidly gain information about prey and to successfully locate their preferred prey on their own.”

“Innate preference is beneficial as it increases efficiency in prey capture,” adds Cárdenas. “It is, however, important that spiderlings hatch near to a place of high ant occurrence, such as ant paths.”

More great egrets wintering

This is a video from the Czech republic about a great egret and grey herons.

According to warden Martijn van Schie, about 270 great egrets winter now in Nieuwkoopse Plassen nature reserve in the Netherlands.

That is more than ever.

Diet variability in the White Stork Ciconia ciconia in eastern Algeria

Originally posted on North African Birds:

Cheriak, L., Barbraud, C., Doumandji, S. & Bouguessa, S. 2014. Diet variability in the White Stork Ciconia ciconia in eastern Algeria. Ostrich 85: 201–204. doi:10.2989/00306525.2014.971451

PDF disponible maintenant sur African Journals online.


The diet of the White Stork Ciconia ciconia was studied at El Merdja, Algeria, from 1997 to 1999 and in 2007 by analysing 240 regurgitated pellets. A total of 12 234 prey types were identified and classified into six categories. Insects dominated during each month and year of the study. Three orders of insects were mainly consumed. Coleoptera species were the most frequently consumed prey during all months and years, followed by Dermaptera species, except in 1998 when Orthoptera were more frequent. The frequency of families of prey insects varied considerably depending on the year: Carabidae were dominant in 2007, Tenebrionidae in 1999 and Carcinophoridae in 1997.

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Belgian bat news

This is a particoloured bat video from the Czech republic.

Bat researchers in Belgium report (translated):

Friday, November 21, 2014

The particoloured bat is a maverick amomg our native bat species. With barely forty sightings in Belgium it remains a very rare visitor. But there seems to be improvement coming: for 2014, the counter says eight observations. This autumn, the species was already observed seven times, and that’s a record. However, we should not just assume there is improvement because recently people have started to observe slightly more than previously.