Summer has turned into autumn, and our lapwings (as expected based on last year’s experience) have once again started moving after a long period of immobility. Andreska, Brusinka, Lulu, and Gouda headed to France, while Cirkulárka (perhaps motivated by the increasing density of French fields filled with newly arriving companions) was the first to cross the Bay of Biscay and reach Spain. While we can expect further movements from the lapwings any day now, the last remnants of battery power are, as usual, fading from the woodcock transmitters, and it is almost a miracle when any of them still sends a signal. For now, the woodcocks appear to remain in place, and we will have to wait a bit longer for migration.
So today, after a long time, we will turn away from lapwing transmitters (and transmitters in general) and focus on woodcocks. Specifically, on an aspect transmitters don’t really help us with woodcock nesting behavior. And not only will we not be talking about data gathered through transmitters, but our own field observations will not play the primary role either, although they will come into play. You may ask: how can we learn more about the nesting of a species whose nests can be found only by great chance, or through immense effort? The answer is surprisingly simple! Just browse the internet and admire the photos of those lucky enough to have stumbled upon a woodcock nest and decided to share their find with the world. And since the world is large, and lucky people are many, the internet can reveal to us many woodcock secrets (and surely not only woodcock ones).
But let’s start from the beginning. Naturally, we initially wanted to find nests ourselves and conduct research directly on them. So we set out into the field, walked, searched and found! We found a nest, and encouraged by this success, we went into the woods again the following season, brimming with plans. Again, we walked, searched, and again found a nest, and later another, already hatched. During these trips, we combed vast forest areas in dense lines, back and forth. For it is nearly impossible to find a woodcock nest other than by flushing a perfectly camouflaged incubating female from underfoot. Besides sore knees, we did bring home many other beautiful experiences that nature always offers, but soon we had to admit this approach would not yield large datasets. And even though in subsequent years we occasionally came across nests discovered by other colleagues, the realization remained unchanged: this path was not viable.
Still, by monitoring two nests, we were at least able to publish a description of incubation rhythms of the woodcock (Trejbalová et al., 2023). What is interesting about these rhythms is the precision with which the incubating female organizes her monotonous duty (Fig. 1). Rising at dawn to take her first recess and taking the last one at sunset is one thing. But the fact that she also holds quite strictly to the number and timing of several other recesses during the day is rather striking. And when you look at how precisely she times short nighttime interruptions in incubation (Fig 1A, probably just stretching stiff legs without leaving the nest, perhaps turning slightly), your mind truly boggles. Her persistence to stay on the nest until the very last moment (which makes finding woodcock nests so damn difficult) is further shown by the fact that in Figure 1(B) there is no sign of reaction even to a wild boar troop, which on the very first night after discovery so thoroughly inspected the nest’s surroundings that their snouts even managed to overturn the camera we had placed less than a meter away. And then you try working with such material!
Figure 1: Actograms based on datalogger measurements, showing incubation rhythms at both nests. The x-axis represents time of day. In place of the y-axis, individual days are shown as dates. The orange line represents the ambient temperature measured by the DHT next to the nest, the red-yellow line represents the temperature in the nest. The red sections represent the temperature during the incubation session and the yellow sections represent the temperature during the incubation gaps. The dark blue line represents the humidity in the nest. A) Short gaps of incubation during the night, B) The period when the pigs were moving around the nest, but the woodcock was still sitting on the nest.
What Next?
So how do we move forward in studying woodcock nesting biology? Fortunately, we realized there is a way. And researchers don’t even have to leave the warmth of their homes! Stumbling upon a woodcock nest is not a memorable event only for seasoned ornithologists but for practically anyone who happens to flush one from underfoot with its noisy takeoff. Only a complete ignoramus would not look down and wish to preserve the memory of such a treasure. And today, nothing is easier than capturing that memory on a mobile phone. Thus, such data are abundant. All it took was scouring every corner of the internet, searching in all languages spoken across the vast breeding range of the woodcock for terms like “nest” or “eggs.” Soon we had amassed about five hundred nests, covering nearly the entire range—from peculiar island populations on the Canaries and Azores to Sakhalin and Japan (see Figure 2). Only most of Siberia remains poorly represented, but that can’t be helped.
Figure 2: Map of nest locations whose photographs were obtained from open online sources, shown against the breeding range of the Eurasian Woodcock (in yellow). Map adapted from Sládeček et al. 2025.
This constitutes (as far as we know) the most extensive set of images of woodcock nesting ever assembled and analyzed. And what can a photo taken by a casual mushroom picker, who flushed a woodcock and shared the snapshot online, tell us? You might be surprised; it’s quite a lot! First of all, we know where and when in the season the woodcock nested. The plants around the nest (including dry leaves and twigs) tell us about habitat selection and exact nest placement. We see what material was used to line the nest. We see how many eggs were laid. From several photos of nests with freshly hatched chicks, we learned that unlike most waders, the woodcock does not remove eggshells during hatching but leaves them in the nest even after it has been abandoned.
Today, however, we’ll focus on two details whose importance may seem doubtful at first glance. 60 % of nests (or their immediate surroundings) are marked with droppings, and in even more cases (67 %), woodcock feathers can be seen around the nest in varying amounts (Sládeček et al., 2025).
Why the Mess Left Behind by a Flushed Female?
So, the flushed female often leaves droppings and feathers near the nest. Why should we care? From the bird’s perspective: a nest is a treasure to be guarded. Since predation is the most common cause of nesting failure, most adaptations during breeding revolve around hiding or defending the nest. These phenomena must be seen in that light. In particular, the woodcock is the only species known to defecate on or near the nest when flushed. This is known also in ducks, where it is compounded by the fact that incubating females more or less fast, and their droppings are therefore especially foul-smelling—and, logically, unappealing to an intruder. Traditionally, researchers (as typical intruders themselves) assumed that by defecating on eggs, ducks protected nests from predation. But experiments and observations have not really supported this. For most predators, even dirty eggs were not disgusting enough to spare them.
On the contrary, the presence of droppings (and feathers!) may have the opposite effect: helping predators locate the nest. Droppings can provide scent cues, which birds otherwise strive to minimize around the nest even changing the composition of uropygial gland secretions to produce less volatile diesters (Reneerkens et al., 2002). Obvious uric acid spots (reflecting in UV), as well as conspicuously pale feather undersides, can serve as visual cues for diurnal, sight-oriented predators (see Fig. 3). So it is highly unlikely that a defecating female has the nest’s best interests in mind. Why then does it happen so often
Figure 3: Examples of analyzed photographs:(a) nest with eggs soiled by droppings (photo: Miroslav E. Šálek), (b) nest where only the surroundings are soiled with droppings (source: eBird; photo: Stephen Carter), (c) nest with several small visible feathers (photo: Karel Pithart), and (d) female Eurasian Woodcock incubating a nest with clearly visible droppings (and one feather) around the nest (source: Instagram; photo: Aniuta Gorchakova). Figure adapted from Sládeček et al. 2025.
Most likely, the female’s own survival is at stake rather than the nest’s. As noted above, females rely on camouflage until the very last moment. That can pay off, as in the case of the boar visit described earlier! But if she finally decides to flee, the takeoff must be full throttle. Given the woodcock’s clumsy start, it’s sheer luck if predator jaws snap on empty air. For such performance, the sympathetic nervous system must be activated quickly, mobilizing the body. Such activation brings many changes, and defecation or feather release may be side effects like stress-induced hair loss in humans or acute diarrhea and urination in primates (including us). Dian Fossey, in Gorillas in the Mist, vividly described similar stress responses in gorillas.
So, can droppings or feathers actively help the escaping female, or are they merely harmful side effects? One proposed benefit is weight reduction. But given that defecation reduces body mass by barely 1%, this is unlikely to matter. A second idea is that she might hit the predator directly. A “hot shower” might delay pursuit a strategy perfected by colonial fieldfares (Turdus pilaris), which sometimes so thoroughly plastered raptors with droppings that the birds needed rescue (Bezzel, 1975). But such power cannot be expected from a solitary woodcock.
A third hypothesis seems most plausible: falling droppings (and perhaps fluttering feathers) may distract the predator’s attention, even momentarily. Swedish researchers likened it to a squid’s ink cloud (Lindström & Nilsson, 1988). Of course, such an effect only works in daylight.
In Conclusion
To summarize: woodcocks do their utmost to conceal their nests. If they are flushed and must flee, the presence of droppings and feathers often makes the nest more conspicuous, decreasing its chances of survival. Perhaps this is why woodcocks often abandon nests after being disturbed (Hoodless & Coulson, 1998).
What personal lesson can we take? If you are lucky enough to flush a woodcock (or another rare, secretive nester) from a nest, consider gently removing any droppings or feathers left behind. And since you startled the bird anyway, at least take a quick photo of the nest and share it. Someday, that photo might become a valuable piece of the puzzle of understanding!
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