Marsh Owl

Just over 100 km south of the Strait of Gibraltar, in Morocco, a narrow channel divides sand dunes formed by Atlantic gales. Seawater meets freshwater from several small rivers, creating a lagoon 7 km long and 3.5 km wide. Its name – Merja Zerga – means ‘blue lagoon’. Arnoud and Cecilia have been visiting the area for decades. Slender-billed Curlew Numenius tenuirostris used to be the main attraction until it became extinct. Since 1995, the lagoon’s most endangered bird has been Asio capensis tingitanus, the isolated northern subspecies of Marsh Owl. Morocco’s human population is growing fast, and some 8000 people live in small villages scattered around the lagoon. Most earn a living from fishing, livestock, and by making mats from rushes. A handful try to earn a few extra dirhams by flushing Marsh Owls out of their roosts, and even breeding sites, for any visiting birder unscrupulous enough to pay. 

In CD3-01, it is dusk. A breeding pair croaks in flight, their voices overlapping at the start. Marsh Owls do not hoot, and these short strophes of irregular length croaks are their most important vocalisation. Let’s call them ‘song croaks’. The owls croak at roughly 20-second intervals, nearly always in flight. Individual variation is strong but each owl’s song croaks are consistent and recognisable, especially regarding the rhythm at the start. 

During the breeding season, Marsh Owls croak as they make long display flights in wide circles with deliberate wingbeats and periodic wing-clapping (Smith & Killick-Kendrick 1964). 

Curiously, none of Arnoud’s 84 recordings of Moroccan Marsh Owls contain any wing-clapping. Matt Pretorius from South Africa who knows Marsh Owl A c capensis well, having worked with African Grass Owls Tyto capensis in the same habitat, tells me that wing-clapping is commonest just before and during the breeding season. He adds that if a predator or a researcher flushes a Marsh, it may wing-clap aggressively at any time of year. In Matt’s experience, Marsh only gives single claps like Long-eared Owl, not volleys as in Short-eared Owl. 

Marsh Owl is the African ecological equivalent of Short-eared Owl, and a very close relative (Wink et al 2009). Both live in open habitats and nest on the ground. There have been no detailed studies of Marsh Owl sounds, but I hear many parallels with Short-eared. Despite their very different timbre, Marsh song croaks and Short-eared hooting share some obvious similarities, such as their temporal pattern, including the long silences in between. Both are normally given in flight. 

Marsh Owls are social, sometimes breeding in dense clusters of territories. Suitable habitat is often limited, sometimes leading to the formation of loose colonies (Carlyon 2011). They are also well known for roosting communally. In CD3-02, recorded in October, at least two owls fly out of their roost. There is one croak at close range, then by the time other croaks follow the owls are already distant.

Both sexes produce song croaks. According to Fry et al (1988), the female’s voice is higher-pitched and softer than the male’s. In CD3-03, from the main courtship period in March, a male and female are emerging from their breeding territory at dusk. In this recording, any pitch difference between the two individuals is negligible and I hear no difference in timbre or ‘softness’, so I have left them unsexed.

Marsh Owl’s soliciting call is a short rising croak, equivalent to the rrrrAh of Short-eared Owl. In Arnoud’s recordings of this sound, the caller was always perched. In CD3-04, it is egg-laying time and a presumed female Marsh gives a series of rising croaks at dusk. 

Hamida Hammouradia, a warden at Merja Zerga, made a special effort to find a Marsh Owl nest for Arnoud. When he succeeded, Arnoud and Cecilia immediately drove down from the Netherlands to Morocco. When Hamida showed them the nest, it contained three young around 12 days old. Arnoud left his equipment recording there for a couple of hours and moved to a respectful distance. Two days later they had dispersed into the grass, just like two-week-old Short-eared Owls.

During the last half hour of Arnoud’s recording session, adults landed at the nest six times. In CD3-05 one, probably the female, gives a song croak before landing, and then walks into the tunnel in the grass where the nest is situated. Once at the nest she starts giving rising croaks while the nestlings beg with high, rising whistles. These begging calls almost certainly develop into the rising croaks of adults. In the background the other adult gives a series of descending growls from a perch nearby. Arnoud recorded these growls most frequently when he was close to the nest, both from perched and flying Marsh Owls. They were usually single (CD3-06), but with increasing excitement they could be grouped into short, fairly rapid series (CD3-07).

In CD3-08, an adult that has just brought prey to the nest gives a series of very quiet, low-pitched croaks. These are Marsh Owl’s feeding calls. The youngsters in the recording respond with begging calls, but they also produce some chitter calls, signalling discomfort. 

During the same trip to Morocco, Arnoud recorded a family of Marsh Owls at Oued Loukkos, a freshwater marsh 35 km to the north. Oued Loukkos has long been known for Marsh Owls, although this was their first breeding record for many years. The juveniles in CD3-09 were among three that had already learned to fly and were perched on fence posts along the edge of the marsh. 

Nowadays, Marsh Owl barely clings to survival in north-western Africa, and it may become extinct there without stricter protection. The population was certainly healthier in recent history, but would have been common thousands of years ago, when the Sahara received more rainfall than at present. A major study of Saharan conditions 6000 years ago, based on pollen and plant macrofossil data, identified only two sites in southern Egypt that were desert at that time. “All other Saharan sites were either steppe, at low elevation, or temperate xerophytic woods/scrub, or even warm mixed forest in the Saharan mountains” (Jolly et al 1998). Marsh Owl’s North African heyday probably ended around the time of the ancient Egyptians when the desert gradually expanded to its current size, and most forms of life were pushed towards its fringes.

As recently as the late 19th century, Marsh Owl showed up regularly in Europe. M F Favier, a French collector who died in Morocco in the mid-19th century, described Marsh Owl as “a common resident near Tangier, usually frequenting wet swampy ground, feeding chiefly on insects. Some pass over to Europe in March and April, returning in November and December” (Irby 1895). In Cádiz, Spain, Howard Irby found eight Marsh Owls, up to three at a time, “within a space of about a square mile”. He flushed them all while hunting snipe in October and November, but others also found them there during the winter months. March, May and August visits failed to produce any owls (Irby 1895). This hotspot probably concerned a roost, but elsewhere in Iberia there are suggestions that the owls may even have bred.

One of my favourite owl recording locations in Portugal is Pancas on the Tagus Estuary. I have sound-recorded seven species there, including Short-eared Owl. In the 19th century there was an eighth. Dom Carlos de Bragança, a keen collector who happened to be the king, shot two Marsh Owls at Pancas in his youth, one in December 1887 and the other in January of an unrecorded year. In February 1908 he suffered the same fate. According to Dom Carlos, Marsh Owl was a sedentary species, and “one or two could always be found in the marsh at Pancas, in summer or winter” (Carlos de Bragança in Catry et al 2010). 

It was almost dark when Arnoud returned to pick up his equipment from the nest that Hamida had found. As he reappeared some distance away, an adult went out with a growl and flew some distance away. CD3-10 documents what happened next. First we hear Arnoud moving through the sedge. Then there are some high-pitched squealing sounds, moving fairly rapidly from left to centre. Arnoud assumed that this sound was coming from the young, since the adult had flown some distance away. However, the rapid movement does not fit easily with a nestling and we never recorded those sounds at any other time. With the benefit of hindsight, I suggest that an adult approached unseen by Arnoud and performed a distraction display to try to lure him away from the nest. The sounds are remarkably similar to distraction sounds of other Asio owls (cf, CD2-72 & CD2-87).

Like Dick on his return visit to the Short-eared Owls, Arnoud may not have been treated to the full distraction display. According to Smith & Killick-Kendrick (1964), adults disturbed at a nest with well-incubated eggs or tiny young will fly around in tight circles “and then crash to the ground, flapping in the grass and uttering a noise that is best described as a squeal.” According to Joubert (1943), adults disturbed at their nest fly round with croaks and a feeble whistle, and much bill-snapping. Matt Pretorius tells me that distraction displays are often preceded by wing-clapping. 

After they leave their parents, Moroccan Marsh Owls do not have to disperse very far. The coastal wetlands usually offer sufficient food all year round, even during the dry season. In Sub-Saharan Africa life can be much more difficult. There, the owls often make nomadic movements in search of food and sometimes even follow bushfires, preying on termites and other insects fleeing the flames (Kemp 1987). Breeding takes place when productivity is highest at the end of the rains, and before the worst of the drought. This also applies for Morocco, where the rainy season is from November to March.

Marsh Owls eat a great many insects and arachnids. At some sites in Morocco they also focus on rodents, but at Merja Zerga they hunt birds. During late summer and early autumn, the driest season, migrants pass through in great numbers. Many also stay for the winter. Keijl & Sandee (1996) listed Common Quail Coturnix coturnix, Dunlin Calidris alpina, small chats and warblers, and possibly even Richard’s Pipit Anthus richardi in their early November diet, while Bergier & Thévenot (1991) mentioned birds as large as Water Rail Rallus aquaticus, European Golden Plover Pluvialis apricaria and Common Redshank Tringa totanus. The owls hunt mainly at night, suggesting that they snatch some of the passerines from their roosts, before returning to their own roost around an hour before dawn. 

On 6 October 2007, Arnoud was ready for them. The cockerels were wide-awake, but the villagers were still sleeping off the previous evening’s Ramadan feast. In CD3-11, the first owl to return is the same as the first one out the evening before (cf CD3-02). As the Marsh Owls settle into their roost, some Cucumiaus Athene noctua glaux have the last word, scolding the bird hunters in their midst. 

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