Sugarbirds are medium-sized nectar feeding birds that are endemic to southern Africa. There are two species of sugarbirds – the Cape Sugarbird and the Gurney’s Sugarbird. Sugarbirds have long tails and curved bills that allow them to feed on nectar from flowers. Their bright, colorful plumage makes them stand out. Sugarbirds play an important role in pollinating plants in the regions where they live. A question that often comes up regarding these unique birds is whether they migrate or stay resident all year round. In this article, we will examine the evidence and research on sugarbird migratory patterns and behavior to determine if sugarbirds truly migrate.
Sugarbird Habitats and Ranges
To understand if and how sugarbirds migrate, it is important to first look at where they live and their ranges.
The Cape Sugarbird has a range that extends across southwestern South Africa, from the Cape Peninsula northeastwards to Port Elizabeth. Its habitat includes fynbos, a unique shrubland ecoregion that only exists in southwestern South Africa and is their primary feeding ground.
The Gurney’s Sugarbird has a more restricted range in KwaZulu-Natal province in southeastern South Africa. Its habitat consists of mistbelt forests and grasslands in higher altitude upland areas.
The habitats and climates where Cape and Gurney’s Sugarbirds live are relatively mild year-round, without extreme shifts in temperature and resources between seasons. This suggests sugarbirds may not need to migrate due to sufficient food availability. However, their ranges do experience some seasonal variation that could potentially impact resources.
Sugarbird Diet and Feeding
Sugarbirds have specialized diets, feeding almost exclusively on nectar from flowers. They use their curved bills to probe into flowers and drink the nectar inside. Sugarbirds also eat some insects and spiders to obtain protein, which they capture by hawking.
The key food source for Cape Sugarbirds is nectar from Protea species flowers native to fynbos. Proteas flower primarily in winter and spring. For Gurney’s Sugarbirds, their key food is nectar from aloes, which flower in winter.
This reliance on nectar from seasonal flowering plants suggests that sugarbirds could migrate if food becomes scarce outside of peak flowering periods. However, these seasons have some overlap that may provide year-round food resources.
Sugarbird Breeding Seasons
The timing and location of breeding seasons can provide clues into migratory behaviors of birds. Cape Sugarbirds primarily breed from March to August, which overlaps with protea flowering season. Gurney’s Sugarbird breeding season is earlier from December to April, also overlapping aloe flowering.
Sugarbirds appear to time their breeding to match peak food availability. Their relatively fixed breeding seasons suggest sugarbirds are resident and do not spend parts of the year away from breeding grounds, unlike migratory species.
Banding and Tracking Studies
Banding and tracking individual birds is one of the most definitive ways to study migratory patterns. Although limited, some banding evidence exists for sugarbirds.
One Cape Sugarbird was banded as a nestling in Kirstenbosch National Botanical Garden and sighted 12 years later in the same area. Banding of Gurney’s Sugarbirds at Oribi Gorge Nature Reserve has revealed they regularly return to the same area.
A tracking study of Cape Sugarbirds using GPS devices showed they maintain stable home ranges of 2-5 hectares through the year, not moving more than 7 km from nesting sites. This territorial behavior does not indicate migratory movement.
While minimal, banding and tracking supports the idea that sugarbirds are resident within protected areas and do not make large seasonal movements.
Population Patterns
Counting and comparing seasonal populations can determine if numbers change drastically, suggesting possible migration. However, population surveys for sugarbirds are limited.
For Cape Sugarbirds, some evidence indicates higher densities during protea flowering season, possibly due to influxes from other areas. But there is no data showing major drops in populations in non-flowering months.
For Gurney’s Sugarbirds, seasonal differences in populations within protected areas have not been observed. More long-term, consistent surveys are needed to definitively determine if populations fluctuate.
Overall, evidence does not point to major seasonal shifts in sugarbird numbers that would be expected with migration. But more thorough monitoring is required.
Adaptations for Migration
Most migratory birds have adaptations like long, pointed wings for efficient long-distance flight. Sugarbirds do not appear to have these morphological specializations. Their short, rounded wings are suited for brief, maneuverable flights between nectar sources, not sustained travel.
Sugarbirds also have high site fidelity, regularly returning to and defending the same feeding territories. These territorial behaviors do not align with migratory lifestyles where birds inhabit different areas in different seasons.
Lack of migration-optimized features suggests sugarbirds do not make predictably lengthy migrations.
Conclusions
After examining the available evidence, sugarbirds are considered resident, non-migratory species. Key points supporting this conclusion include:
– Breeding timed with peak food availability
– Site fidelity and territorial behaviors
– Lack of seasonal fluctuations in populations
– Morphology not suited for long flights
However, more research is still needed to conclusively determine migratory status, especially tracking and population studies. The possibility of smaller scale movements between habitat patches in search of food cannot be ruled out. But evidence does not support large, seasonal migrations for Cape and Gurney’s sugarbirds. Their resident status aligns with their specialized diets and habitats. Overall, it appears nature has designed sugarbirds to live year-round in the areas they call home.