Short-eared Owl

Short-eared Owls Asio flammeus are complete bastards to record. They hoot mainly in flight and often at a great height. Getting close is almost impossible; you can’t just leave a recorder near a songpost. If one hoots right overhead, its next series of hoots will seem far away. We all had a go at one time or another, for the best part of a decade. On the island of Texel, where Arnoud and I tried for several years to record them, they hoot in the late afternoon. Parachute jumpers, the Royal Dutch Air Force, car and bicycle traffic all conspired against us. I finally succeeded while revisiting another island, after realising that they also hoot at dawn and in the middle of the night. 

When I was a child I spent all my summer holidays in Orkney. As we travelled round the islands, I learned to pay attention whenever pasture gave way to rough grassland or bog. Often a Short-eared Owl would be perched on a fencepost or a Hen Harrier Circus cyaneus would be skimming the tussocks on raised wings. Orkney supports the UK’s only Common Voles Microtus arvalis, brought from the continent in Neolithic times (Haynes et al 2003). Not only are they abundant, but since arriving in the archipelago they have increased in size. Orkney has no natural ground predators, which benefits not only the voles but also ground-nesting birds like Short-eared Owls. Given such advantages, it is no surprise that Orkney has one of their healthiest populations in north-western Europe.

In 2010 I took my own family on holiday to Orkney for the first time. By day we shared the pleasures of beachcombing and singing to Grey Seals Halichoerus grypus. By night I went off to record Short-eared Owls. In order to minimise disturbance, I left the recording equipment in a well-chosen spot and went back to get some sleep. There were two pairs that I could follow. One already had tiny nestlings so the male was not hooting very much. The male of the other pair was still displaying. In CD2- 77, he gives several volleys of quiet, low-pitched hoots. As he passes out of earshot, a Eurasian Curlew Numenius arquata sings. Then he is back, with only a distant Sedge Warbler Acrocephalus schoenobaenus for company as he hoots right overhead. 

Nearly two hours later, the male flies over again while performing a different display flight (CD2-78). Although it is only 02:53, the dawn chorus is well underway, and curlews ripple gently in all directions. Over this murmur, the owl gives four series of hoots interspersed with rapid volleys of wingclaps. During the long gaps, a Common Snipe Gallinago gallinago drums close by, and a Red Grouse Lagopus scotica displays in the distance.

Like many other ground-nesting birds, male Short-eared Owls use altitude to project their sound and to be seen. Think of a skydancing Hen Harrier, or a Eurasian Skylark Alauda arvensis singing as a speck up in the sky. Curiously, their wing-clapping often seems to project further than their hooting. On the steppes of northern Kazakhstan, I once followed a male displaying until he was so high up that I could barely hear either sound. Wing-clapping at such a high altitude is a courtship display, whereas low-altitude clapping is primarily aggressive.

Aggressive wing-clapping typically consists of one volley or just a few volleys, each of which contains about 10 claps. It occurs during direct, rapid flight where the bird’s obvious intent is to chase another owl, or less often when returning to its territory from a chase (Clark 1975). In CD2-79, a male was recovering his composure after chasing off a Peregrine Falcon Falco peregrinus. Wing-clapping is performed both by paired and unpaired male Short-eared Owls, unlike Long-eared Owl in which only paired males wing-clap (Hawley 1966). It is limited to the breeding season, and autumn wing-clapping is only possible if a freak rodent plague encourages breeding at the ‘wrong’ time of year. In the 1950s, for example, three Dutch pairs bred in December (Bakker 1957).

Treeless habitats and partly diurnal habits make Short-eared Owls conspicuous, so the visual aspect of their displays is highly developed. In courtship flights, the male ascends with characteristic ‘rowing’ wingbeats, which are rhythmic but only moderately deep. He interrupts these now and then to perform wingclaps. “With increasing altitude the male Wingclaps less frequently and does some occasional soaring… The bird intersperses hovers with relatively shallow descending glides that end with a Wingclap. Then he climbs again. The routine generally ends in a spectacular descent with a flight somewhat peculiar to this situation.” This display is called the Sashay flight, “as the bird appears to rock back and forth with its wings held in a deep dihedral” (Clark 1975). 

Display flights are visible continuously, making it possible for Short-eared Owls to economise on sounds, and this perhaps helps to explain why they hoot and wingclap in short volleys. The visual display continues during the long silence between volleys. Physiological limits also play a role. It would be impossible for an owl to maintain flight and give volleys of wingclaps or hoots at very short intervals. No owl that I know of ever hoots in flight for more than a few seconds at a time.

A few weeks after our Orkney holiday, Peter Nuyten was on Ameland, a Dutch island that also offers special conditions for Short-eared Owls. It is the only Waddeneiland supporting Common Voles and since 1984 it has also had Field Voles M agrestis (Broekhuizen et al 1992). Unlike nearby Terschelling and Texel, which have Stoats Mustela erminea, Ameland has no natural ground predators. The pair that Peter recorded seemed intent on nesting on a high dune in an area subject to flooding by the nearby Waddenzee. In CD2-80, the male is hooting at night, with a variety of wetland birds for company.

Territorial displays can have a male calling and wing-clapping as it circles high 600 or 700 m away from a female who responds from the ground. Attempts to record this joint display have frustrated us the most. While we don’t have an example that captures the three dimensional scale and distance, we do have a closer version of it. In CD2-81, the Ameland male hoots several times as he arrives with prey. The female replies with rrrrAH soliciting calls that quickly sound frenzied, as she demands that he hand over the prey. This is the female’s commonest call during the breeding season, equivalent to the Vvvw of Long-eared Owl. 

Male hooting and female soliciting calls are subject to individual variation. The male in CD2-82 belongs to the second pair I recorded in Orkney. Every time this male hooted, his voice had a markedly gruff timbre. In this recording he hoots three times. The female goes out to meet him, giving a very short, slightly descending variant of her soliciting call. 

At other times, the same female gave more typical soliciting calls, often in long series. In CD2-83, she is the bird closer to the microphones. The male arrives at the start, giving a couple of quiet, low grumbles. Then he perches at a distance and at 0:25 and 0:34 he replies to the much closer female with his own slightly lower-pitched soliciting calls. After a short series of hoots at 1:02, he eventually brings food to the nest. We hear his wingbeats and the female’s increased excitement as he approaches. 

Clark (1975) could distinguish male and female soliciting calls at four different nests, the male sounding lower-pitched and more disyllabic than the female, with a more rasping first syllable. In CD2-84, the male is the closer individual that calls once at the start, and the female replies several times. For me the only striking difference is in their pitch.

Male Short-eared Owls sometimes use their soliciting call in territorial defence displays, the two most important of which are the ‘Underwing’ and the ‘Skirmish’ (Clark 1975). In the Underwing, the male flies around with exaggerated wingbeats, raising his wings high above his back to show their whitish undersides to his rival. Males often use this low-intensity display to reinforce their mutual territorial borders. In the Skirmish, the rivals fly up at one another, presenting their talons if the encounter becomes more intense. In extreme cases, talon-locking with spiralling falls may result.

Traditionally, up to 10 subspecies of Short-eared Owl have been recognised (del Hoyo et al 1999). Based on starkly contrasting soliciting calls, they can be placed in two groups. A f flammeus is the Short-eared Owl of northern Eurasia and North America. Most of the others live in or near the Caribbean and South America, except for sandwichensis of Hawaii and ponapensis of the Caroline Islands, Micronesia, the only one for which I could find no recordings. On vocal grounds, there is evidence for a northern group with rising rrrrAh soliciting calls and a Caribbean/South American group with very different-sounding, tomcat-like, moaning soliciting calls. CD2-85 is an example from the latter group: subspecies sanfordi, endemic to the Falkland Islands. By contrast the even more isolated sandwichensis, known in Hawaii as the Pueo, has a flammeus-like soliciting call and presumably evolved from northern stock.

None of the southern group have ever occurred in the Western Palearctic. Besides sanfordi, they include domingensis and portoricensis of the Greater Antilles, bogotensis, pallidicaudatus and suinda of continental South America, and the isolated galapagoensis of the Galapagos Islands. Through most of Latin America, they are called ‘lechuza campestre’ or ‘búho campestre’, both of which translate as ‘field owl’. The oldest named southern taxon is domingensis so in the event of a split, we can call the southern species Field Owl A domingensis. 

In Orkney, Short-eared Owls are called ‘Cattie-face’. The female of the second pair I recorded there gave soliciting calls to demand voles whenever the male appeared. After taking one, she would encourage her tiny nestlings to accept little morsels with her ‘feeding calls’ (CD2-86). These are quiet calls, probably impossible to hear under normal field conditions. The rhythmic pattern of feeding calls is similar in all owl species. 

During the two nights I spent recording this family, one week apart, they were constantly fighting with a Peregrine Falcon. I am not sure whether the Peregrine, a known predator of Short-eared Owls (Mikkola 1983), was actually targeting the owls or simply passing by. In CD2-87, the female attacks the Peregrine ferociously. As she takes off from the nest, two tiny young peep quietly for a few seconds. There is a harsh, descending bark from the female followed by the whoosh of the Peregrine’s wings. The female barks several more times and snaps her bill loudly at the enemy. From 0:15 the Peregrine calls and the owl gives two last barks. Gradually calm returns.

The reaction to ground predators is very different. Like waders and other birds that nest on the ground, as well as a few owls that don’t, Short-eared Owls have a well-developed distraction display. Dick witnessed this while approaching a nest in Lapland where the young were in the process of hatching. The male came flying in through the trees and threw himself on the ground, dragging his wings. The next day Dick was better prepared, but the display was less intense. In CD2-88, the calls are all given in flight, not on the ground, but I still find them impressive. 

The dangers of nesting on the ground are so great that Short-eared Owls flee into the vegetation like young waders at the precocious age of just two weeks. They can move surprisingly far in just a short time, eg, 175 m in just four days (Clark 1975). Begging persistently and loudly like a Long-eared Owl is not an option, so their calls are weaker and saved largely for when an adult arrives with food. To help adults locate them quickly, the owlets ruffle the body feathers and vibrate their wings close to the body. “As the intensity of begging increases, the owlet extends and flutters the wings. Finally, at full intensity, the fully extended wings are rotated so that the ventral surface is directed forward (showing the lighter coloration of the underwing to the approaching parent), and are fluttered in this position almost to the point of flapping” (Clark 1975). As soon as they stop this display, their grass-like camouflage makes them virtually invisible once again.

Begging calls of juvenile Short-eared Owls have a rising intonation, like the soliciting call of adults (CD2-89). By contrast, those of Field Owl have the same descending contour as the adult’s moans. Each taxon’s begging call probably develops into its adult soliciting call. In CD2-90, a juvenile sanfordi gives a continuous stream of begging calls, while an adult barks in excitement. 

After learning to fly, Short-eared Owls lose none of their wanderlust. They are among the most nomadic of owls, flying long distances in search of abundant food supplies. A few even cross the Sahara, the only WP owl other than Eurasian Scops Owl Otus scops known to do so. With movements like this, it is not surprising that Short-eared Owls have reached far-flung oceanic islands like Hawaii. More surprising perhaps is that apart from Iceland, they have not colonised any of the more distant North Atlantic islands. They do turn up from time to time in the Azores, and it is not impossible that they bred in the Selvagens before the introduced House Mouse Mus domesticus population was eradicated (Rafael Matias pers comm). A century ago, breeding was also suspected on Porto Santo or associated islets in the Madeira archipelago (Bannerman 1965). 

Over the last few autumns I have been visiting the tiny island of Berlenga, just off continental Portugal. By day I count migrants and search for vagrants; by night I listen to nocturnal migration and the odd Grant’s Storm Petrel Oceanodroma. During my first autumn visit, I was thrilled to hear Short-eared Owls in the dark. There were at least two on the island, and a month later there were six. Berlenga has many Black Rats Rattus rattus, presumably the main attraction for the owls. It is thrilling to hear the occasional storm petrel and owl duet on Berlenga, a combination I never managed to capture in a recording. The calls I hear there in autumn are mainly variants of the soliciting call and a coarse barking sound similar to the one Short-eared uses when mobbing a raptor. Elsewhere, it is not uncommon to hear calls like these whenever several of the owls winter together in a restricted area.

My most magical Portuguese encounter with Short-eared Owls took place one autumn night when I went to record migration in the hours before dawn. At the end of a peninsula called Cabo Espichel, there is a picturesque former convent. I sat under its walls hoping to hear migrating passerines and maybe see a few lit up in the floodlights. Surprisingly, it was five Short-eared that I saw, flying in slow, untidy circuits, high above the convent. Now and then when they met in mid-air, they gave a very faint, high-pitched tinkling sound unlike anything I have heard at any other time. 

I began to suspect that like me, they were there for the migrating passerines. When a Song Thrush Turdus philomelos came in off the sea, two of them went for it. Later, I read Canário et al’s (2012) account of exactly the same behaviour at Sagres, the south-western corner of Portugal. Arnoud also saw Short-eared Owls catching passerines near a lighthouse in the Netherlands (van den Berg 1974).

Short-eared Owls do not breed in Portugal, so they were migrants too. In a week or two the songbird passage would be over and they would have to hunt elsewhere. Would they stay in Portugal, or might they head south for a meeting with their darker, more raucous African cousin?