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Despite modern methods that include bird ringing and satellite tracking, our understanding of the dynamics of how birds orientate and achieve sometimes truly global endeavours still remain unresolved, making it an exciting field of study for both academics and novices alike. A classic example of one of these anomalies is the dynamics of how the Barn Swallow shows an innate ability to navigate over continents during the non-breeding season to Southern Africa but find their way back to the same individual nest sites under British, French or German rooftops each year.
Globally 40% of all birds undertake a bi-annual journey, normally one southward and one northward, that varies in length between species and even between different populations within a single species. These marathons often present countless perilous dangers along the way and over a billion individuals die each year from predation, drowning or exhaustion.
Generally, birds migrate either to avoid unfavourable or even fatal conditions or to take advantage of particularly rich feeding or nesting grounds brought on by the annual fluctuations of the seasons.
From a South African perspective, a nation that receives many such visitors, making it one of the best birding destinations in the world, migrants tend to originate from three different sources:
- Intra-African migrants move within the continent often oscillating north and south over the equator and include birds such as Woodland-, African Pygmy- and Grey-hooded Kingfishers, Southern Carmine Bee-eater, 6 species of Cuckoo, Wahlberg’s Eagle and Red-breasted Swallow to name a few. Within Karongwe Game Reserve alone, up to 32 species of this type of migrant have been recorded from the months of November through to March.
- Altitudinal migrants refer to species that move from higher altitude breeding grounds to lower lying regions during the colder winter months and can include birds like Afromontane forest dwellers such as Narina Trogon, Black Saw-wing, Olive Woodpecker and Grey Cuckooshrike as well as montane and grassland breeders such as African Black and Alpine Swifts, Black-rumped Buttonquail, Short-tailed Pipit and Grey-rumped Swallow.
- The most recognizable type of migrants for most tourists visiting our shores are what is known as Palearctic migrants, most of which journey from European, Scandinavian or Middle Eastern nesting grounds and pass through land-bridges such as Gibraltar in Spain and Eilat in Israel These locations act as bottlenecks for thousands of passing birds, while others simply fly straight over the Mediterranean Sea in a single flight in order to take advantage of the subtropical bounty found here during the southern summer. Species such as Common and Great Spotted Cuckoos, European Roller, White Stork, European Bee-eater, Eurasian Golden Oriole, Lesser Spotted and Steppe Eagles, Montagu’s Harrier, Little Stint, Ruff, Red-backed and Lesser Grey Shrikes, Bar-tailed Godwit, Common Greenshank and Spotted Flycatcher are but a few examples of this type of visitor found in the region during the non-breeding season.
An important and much smaller subsection of this class of migrant are those that hail from Siberia and despite only being a handful of species do deserve a mention such as the yakutensis subspecies of Willow Warbler, Curlew Sandpiper and the globally threatened Amur Falcon.
The story of the Amur Falcon Falco amurensis is both a heartbreaking, yet equally impressive one. The entire world population, approximated at 500,000 pairs, migrates from steppe grassland breeding zones in northeastern Russia, northern Mongolia and parts of northern North Korea in late September across the Himalayas and over the Indian Ocean using an island-hopping approach from the Maldives to Seychelles, Mauritius, Comoros and Madagascar to finally end in the grassland and savannah biomes of Southern Africa, before returning in a similar fashion a few months later in a 22,000km round trip.
Some impressive investigative journalism in October 2012 brought to light that on one of the species most important staging grounds in the Indian provinces of Nagaland and Mizoram, traditional hunting involving the slaughter, sale and consumption of between 12,000 and 14,000 birds per day amalgamating to a staggering between 120,000 and 140,000 birds were being killed each year. However within 9 months of the exposure of this practice not only had the local and national government taken action and provided iron-clad legislation protecting the Amur Falcon throughout the country but even some of the very same people involved in the butchery had become the species greatest champions, particularly the youth of the region, advocating its conservation and future success.
Ultimately the human impact on migrating birds whether directly through practices such as bird liming on Mediterranean islands as a singular example or indirect such as the subtle impacts of climate change, many species of migrants are walking an ever-narrowing tightrope and general awareness of this, one of nature’s greatest spectacles, is needed more than ever.
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[av_tab title=’Bird Migration at Selati Game Reserve’ icon_select=’no’ icon=’ue800′ font=’entypo-fontello’]
On the local scale, such as here in the Selati Game Reserve within the Lowveld region, migration and the arrival of each migrant can be in some ways catalogued in a general pattern giving the months of early summer and spring a wonderful progressive character reminiscent of an orchestral composition building from minimalism to a full crescendo. The vast majority of migrants seen on the reserve are from Palearctic or intra-African heritage while altitudinal migrants are rarely recorded or are vagrants to the area.
August is where it all begins, where mid-month there is still chill in the air of some evenings, a remnant of winter, but a general warming tone to the days as time progresses sees the arrival of the first returning birds. These are usually intra-Africans with Lesser Striped and Red-breasted Swallows being part of the first vanguard back alongside Yellow-billed Kite, Levaillant’s Cuckoo and the impressive Wahlberg’s Eagle which takes up residence once again around traditional nest sites. In many cases, these species are also, in fact, the last to leave and really only spend a few months away from the region, nevertheless their arrival after the cold crisp mornings of the previous months is a welcome one.
As September begins to heat up, so does the chance of an early thunderstorm or two, more intra-African migrants continue to arrive such as White-rumped Swift in force, Klaas’s and Jacobin (or Pied) Cuckoos as well as the first Europeans stretching down from across the Mediterranean Sea arrive with European Bee-eater and Willow Warbler often being seen, or at least heard, within the first week of the month. By the end of the month midday temperatures are routinely in the mid 30’s, vegetation is beginning to show signs of growth and the arrivals are thick and fast with Black and the wonderfully plaintive Red-chested Cuckoos usually turning up as well as Marsh Warbler, Common Swift and the first waders like Little Stint, Ruff, Wood and Common Sandpipers and Common Greenshank. Another fantastic element of this period is the annual cycle of several local species from often rather drab winter attire to a vibrant or distinctive breeding plumage. A good example of this is the typical Weaver family which in several species have males that adorn bright yellow, black and green gear and begin to build their world famous nests in noisy colonies often close to water sources. A special of Selati, the Red-headed Weaver transforms from a drab yellowish brown bird to a scarlet-fronted champion often build lonely, singular, scrambling nests in open areas such as on power lines or dead trees. Other species which transform at this time of year include widowbirds, indigobirds and…
October is a turning point for summer migrants in the Lowveld, the changeover from winter to summer species is really in evidence over the weeks with dawn choruses throughout the reserve being bolstered by many fresh additions. The character of the seasons definitely takes a turn this month. African species include; African and the very localised Thick-billed Cuckoo begins to make its presence known. This species parasitizes the resident Retz’s Helmetshrike which favours areas that have dense Mopane groves, a common tree species here on Selati, and the reserve itself is truly one of the best places in Southern Africa to find this scarce brood parasite. A distinctive piercing call and a slow flapping display flight interspersed with glides make this species rather easy to identify and young birds have been known to overwinter both here and at the nearby Karongwe Game Reserve. The lines between late October and early November become blurred in terms of newly returning species, but as the temperature continues to remain warm and in good years, rain will have already arrived in some manner, the vegetation and arthropod communities begin to thrive in full swing. Both Lesser Spotted and Steppe Eagles arrive from eastern Europe by the end of the month giving the now “local” Wahlberg’s some competition but also take advantage of any early termite alate emergences particularly after rain. Other Europeans like Eurasian Golden Oriole, Red-backed and Lesser Grey Shrike, White Stork, European Roller, Olive Tree Warbler and the aforementioned Barn Swallow all pile into the area in good numbers within these few weeks
November is by far the busiest month with most, if not all summering species arriving back by the end of the month. The most anticipated arrival is that of the Woodland Kingfisher, one of the regions “sounds-of-summer” which usually turn up before the middle of the month and rather than drip through in small numbers they seem to arrive all together overnight. Other potential newcomers this month, as well as straggling individuals of species that have already been recorded, include Grey-hooded and African Pygmy Kingfisher, European Nightjar, Lesser Kestrel and Great Spotted Cuckoo. The last migrant to arrive is the globally threatened Amur Falcon from its Siberian breeding grounds and can arrive late in the month or even as late as mid-December.
All of these species enjoy the bounty of the subtropical summer of South Africa’s savannah biome while escaping less ideal or fatal conditions further north across the equator for several months. During this time, some, particularly intra-Africans take the opportunity to breed within the region while others like the Palearctics simply take advantage of the good feeding opportunities brought by the southward movement of the Inter-Tropical Convergence Zone (ITCZ).