The bird and the bees

Forget about man and his dog. A small brown bird called the honeyguide lays claim to one of the oldest relationships between humans and animals, says Mark D Anderson.

SPOTTING THE HONEYS. The male greater honeyguide is identified by its pink bill, black throat and white ear patches. The female has no bold facial markings and she has a blackish bill.

Swainson, 1837

In the old days, people would follow a honeyguide to a wild bee nest, where they would smoke out the bees and rob the nest. The bird’s reward for leading humans to honey would be a feast of beeswax and bee larvae. Scientists suggest that this relationship goes back to prehistoric times when we all still had to forage for our sugar fix. In modern times, honey­guides are still so tuned in to human behaviour that they will even attempt to guide boats and motor vehicles to bee nests.The honeyguide is the only bird species able to digest beeswax, and it has a tough skin to protect it against bee stings.

Honey, I’m here…
If you’re in the bush and notice a small brown bird chattering away to attract your attention and then flying ahead of you, only to land on a nearby bush, you may well have met a greater honeyguide (the one species in South Africa known to interact with humans in this way). Once the bird has got your attention, it will flick its tail, fly to the next bush and wait for you to follow, gradually leading you to a bee nest.

Honey hex
In African folklore there’s a belief that if you fail to reward the honeyguide, it will bring misfortune upon your head, and next time it will show you the way to a black mamba instead of a sweet treat.

Honey who? 
In Kenya, the Boran people still actively use the honeyguide to find honey. The Boran are, however, gradually being excluded from game reserves, leading some scientists to argue that people follow­ing this tradition should be allowed to collect wild honey just to keep this ancient relationship going.

Honeyguides and honey badgers
There is a popular fallacy that honey badgers (and perhaps baboons and mongooses) are also guided to beehives by greater honeyguides. The idea came from early traveller and naturalist Anders Sparrman, who wrote about this in 1785 based on what he had been told. But in the more than 200 years since, no biologist or naturalist has observed this behaviour. So keep your camera and notebook handy – you could be the first person to document teamwork between this bird and an animal other than humans.

  • Friedmann, Herbert (1955). The Honeyguides. U.S. National Museum (Bulletin 208).
  • Short, Lester, and Jennifer Horne (2002). Toucans, Barbets and Honeyguides. Oxford University Press. ISBN 0-19-854666-1.


The Great Green Wall initiative is a pan-African proposal to “green” the continent from west to east in order to battle desertification.  It aims at tackling poverty and the degradation of soils in the Sahel-Saharan region, focusing on a strip of land of 15 km (9 mi) wide and 7,500 km (4,750 mi) long from Dakar to Djibouti.  

Populations in Sahelian Africa are among the poorest and most vulnerable to climatic variability and land degradation.  They depend heavily on healthy ecosystems for rainfed agriculture, fisheries, and livestock management to sustain their livelihoods.  These constitute the primary sectors of employment in the region and generate at least 40 percent of the gross domestic product (GDP) in most of the countries.  Additionally, the ecosystem provides much needed livelihood products, such as fuelwood and bushmeat.  Unfortunately, increasing population pressures on food, fodder, and fuelwood in a vulnerable environment have deteriorating impacts on natural resources, notably vegetation cover.  Climate variability along with frequent droughts and poorly managed land and water resources have caused rivers and lakes to dry up and contribute to increased soil erosion. 

The vision of a great green wall to combat ecological degradation was conceived in 2005 by the former President of the Federal Republic of Nigeria, Chief Olusegun Obasanjo, and the idea was strongly supported by President Abdoulaye Wade of Senegal. The vision evolved into an integrated ecosystem management approach in January 2007, when the African Union adopted declaration 137 VIII, approving the “Decision on the Implementation of the Green Wall for the Sahara Initiative”. In June 2010, Burkina Faso, Chad, Djibouti, Eritrea, Ethiopia, Mali, Mauritania, Niger, Nigeria, Senegal and Sudan signed a convention in Ndjamena, Chad, to create the Great Green Wall (GGW) Agency and nominate a secretary to further develop the initiative. 

The participating countries hope that by linking national-level efforts across borders, they will tackle policy, investment, and institutional barriers that exacerbate the effects of climate change and variability, leading to desertification and deterioration of the environment and natural resources and the risk of conflicts between communities. International Colloquiums are held to discuss possible barriers as well as share available knowledge on the vegetal species, systems of development, and GGW monitoring updates1.

The GEF emulates the spirit of collaboration by allowing participating GGW countries to prioritize which projects they want to implement, in conjunction with GEF agencies and their partners.  They may “develop one or several projects in the context of this program and assign some or all of their financial allocations to the Great Green Wall[1]”.

Progress is apparent especially in the Zinder region of Niger, where tree density has significantly improved since the mid-1980s.  GEF CEO Monique Barbut attributes the success to working with farmers to find technical solutions, particularly long-term land and financial solutions, in order to save the trees.  This form of natural regeneration benefits local communities and the global environment alike by increasing crop yield, improving soil fertility, reducing land erosion, improving fodder availability, diversifying income, cutting wood collection time for women, strengthening resilience to climate change, increasing biodiversity, and much more. 

The Global Environmental Facility (GEF) has granted $100.8 million[2] to the GGW participating countries to expand sustainable land and water management (SLWM) and adaptation in targeted landscapes and in climate vulnerable areas in West African and Sahelian countries.  Each country will design a project based on national-level priorities for GEF and LDCF resources.  The projects will support the following activities
  • Expand investment in SLWM technologies to help communities adapt production systems to climate variability, generate income and livelihoods, secure global public goods (such as retention of greenhouse gases, nitrogen fixation, groundwater recharge and biodiversity), and reduce impacts from erosion, drought, and flooding.
  • Improve land-use planning, such as at watershed scale (i.e. Nigeria) or local levels (i.e. grazing reserves).
  • Improve and apply the information base: climate and water monitoring network improvements, ICT (information communication technology) innovations, institutional cooperation within and across countries, and evidence based policy development
The Great Green Wall of the Sahel, still in the planning stages, will span Africa from Senegal to Djibouti in order to reverse desertification of the Sahel eco-system, and will look much like this image of a local re-forestation initiative in Chad.
The initiative will be ongoing, and has garnered the support of several international organisations including the UK's Royal Botanic Gardens, the World Bank, the African Union, and the UN’s Food and Agriculture Organisation. Together they have pledged $3 billion and the expertise of their botanists for its advancement.
"Examples of success [so far] include more than 50,000 acres of trees planted in Senegal,” says Ryan Schleeter at National Geographic. "Most of these are the acacia species Senegalia senegal, which has economic value for the commodity it produces, gum arabic. (Gum arabic is primarily used as a food additive.) A small portion of the trees are also fruit-bearing, which, when mature, will help combat the high levels of malnutrition in the country’s rural interior.”
Even more dramatic is the project’s potential social impact, says Schleeter. By providing better quality land and more opportunities to earn an income from cultivating it, the Great Green Wall will open up thousands of job opportunities to the local population.

Incorporation of cigarette butts into nests reduces nest ectoparasite load in urban birds: new ingredients for an old recipe?


Birds are known to respond to nest-dwelling parasites by altering behaviours. Some bird species, for example, bring fresh plants to the nest, which contain volatile compounds that repel parasites. There is evidence that some birds living in cities incorporate cigarette butts into their nests, but the effect (if any) of this behaviour remains unclear. Butts from smoked cigarettes retain substantial amounts of nicotine and other compounds that may also act as arthropod repellents. We provide the first evidence that smoked cigarette butts may function as a parasite repellent in urban bird nests. The amount of cellulose acetate from butts in nests of two widely distributed urban birds was negatively associated with the number of nest-dwelling parasites. Moreover, when parasites were attracted to heat traps containing smoked or non-smoked cigarette butts, fewer parasites reached the former, presumably due to the presence of nicotine. Because urbanization changes the abundance and type of resources upon which birds depend, including nesting materials and plants involved in self-medication, our results are consistent with the view that urbanization imposes new challenges on birds that are dealt with using adaptations evolved elsewhere.

1. Introduction

Urbanization is increasingly interesting to biologists as it causes significant changes to species composition, species interactions, and ecological and evolutionary processes [1,2]. Because organisms residing in cities are exposed to different environmental conditions from those in which they evolved, it is relevant to investigate how populations cope with such differences. Parasites affect most aspects of their hosts’ life history and are an important evolutionary force [3,4]. Potential changes in host–parasite interactions as a consequence of urbanization may thus influence which species are most able to exploit urban landscapes.
A variety of parasites cohabit with birds. Of these, ectoparasites are taxonomically widespread, and have severe negative impacts on host condition, reproductive performance and survival [35], both because of their direct effects (e.g. blood-sucking) and indirect effects (e.g. transmission of endoparasites) on avian health. These selective pressures have favoured the evolution of defence mechanisms such as complex immune systems or specific antiparasite behaviours [3,4]. Self-medication is an antiparasite behaviour in which substances produced by other organisms are exploited to increase fitness [6]. For example, some bird species incorporate aromatic plants into their nests, and it has been proposed that the volatile secondary compounds contained therein may either have antiparasitic properties [710] or stimulate the nestlings’ immune system [11].
Urbanization changes the abundance and type of resources available to birds, including nesting materials [12,13]; nest contents of urban birds represent a shift from natural to anthropogenic nesting materials [14]. In nests of some urban birds, cellulose cigarette butts are commonly found [1517]. Butts from smoked cigarettes retain substantial amounts of nicotine and other compounds that may also act as arthropod repellents [18]. Prominent among these is the alkaloid nicotine. This is an antiherbivore chemical derived from the tobacco plant (Nicotiana sp.), and has been used as an arthropod repellent in some crops [19] and for the control of ectoparasites in poultry [20]. Consequently, we hypothesized that cigarette butts may act as an ectoparasite repellent in the nests of urban birds. We conducted field measurements and an experimental field manipulation to evaluate the prediction that the presence of cigarette butts in nests reduces the abundance of nest-dwelling ectoparasites.

2. Material and methods

The study was conducted in an urban population of house sparrows (Passer domesticus; HOSP) and house finches (Carpodacus mexicanus; HOFI) breeding at the campus of the National University of Mexico (UNAM) in Mexico City during the reproductive season of 2011. Both multi-brooded species are widely distributed in cities and are known to incorporate cigarette butts in their nests [15,16].
A thermal trap was placed to attract ectoparasites in nests of HOSP (n = 27) and of HOFI (n = 28) during their second breeding events. This consisted of a battery (12 V/17 A), heating two resistors (37°C) that were situated at opposite sides of the nest. Resistors were fitted with adhesive tape so that parasites became stuck as they reached the source of heat. The cellulose fibres from a smoked (experimental) or a non-smoked cigarette filter (control) were attached to the resistors. To standardize the experimental treatment, smoked filters were obtained from a single 400-pack of regular filter cigarettes (Marlboro) consumed by an artificial smoking device. Traps were left for 20 min in each nest, then the adhesive tapes were collected in individually labelled plastic bags and stored at 4°C until any attached ectoparasite was counted under the microscope (Karl Zeiss Stemi DV4). Nest content (empty, eggs, nestlings) was recorded.
Immediately after chicks fledged, 28 nests of HOSP and 29 nests of HOFI were carefully collected in individually labelled sealed plastic bags and stored at room temperature; nests collected during a week were processed the following weekend. We weighed each nest, assessed the nature and quantity of materials it was composed of, and quantified the number of ectoparasites it contained using Berlese funnels for 24 h under constant temperature and illumination (from a 60 W incandescent lamp; [21,22]). Mites were collected in vials containing 70 per cent ethanol and counted under the microscope as above. We quantified the contribution of cigarette butts as the total weight of cellulose fibre per nest. Ectoparasite abundance was the total number of mites collected. To evaluate differences in ectoparasite abundance between treatments, we used variance component analyses, including nest as a random factor and treatment and nest content as fixed factors. To test for an association between ectoparasite abundance and the weight of cellulose in nests, a general linear model was performed including species as categorical predictor. Analyses were performed using STATISTICA software.

3. Results

HOSP nests were heavier (43.70 ± 24.34 g) than HOFI nests (26.22 ± 12.53; F1,55 = 11.74, p = 0.001). Cellulose from cigarette butts was present in 89.29 per cent of HOSP and 86.21 per cent of HOFI nests, and weighted on average 2.45 ± 3.34 g (range 0–11.75) and 3.06 ± 4.15 g (range 0–14.86) in HOSP and HOFI nests, respectively. On average, HOSP nests included eight (range 0–38) and HOFI nests 10 (0–48) used cigarette butts [23]. Neither the presence nor the amount of cellulose per nest differed between species (all p > 0.55). The number of mites was not different between HOSP and HOFI nests (F1,54 = 0.22 p = 0.64). In both species, parasite abundance was negatively associated with cellulose weight (F1,54 = 17.31, p = 0.0001; figure 1). Traps containing cellulose from smoked butts attracted significantly fewer ectoparasites than traps with non-smoked cellulose (F1,54 = 43.13, p < 0.0001; figure 2). Also, control traps in nests containing eggs gathered more parasites than those in empty nests or in nests with nestlings (F2,52 = 3.74, p = 0.03; see electronic supplementary material).
Figure 1.
Number of parasites, C. mexicanus (grey circles) and P. domesticus (black circles), was a negative function of the amount of cigarette butt material contained in the nest. Asterisk (*) represents regression line from an exponential model fitted to the data from both species.
Figure 2.
Thermal traps with smoked butts attracted fewer mites than traps with non-smoked butts, regardless of the nest content. Non-smoked butts gathered more parasites from nests assayed during incubation than from empty nests or (non-significantly) than after hatching, presumably as some parasites remained attached to the chicks. Probability values from a variance component analysis (global) and from post hoc Bonferroni-corrected comparisons between treatments and nest contents. Probabilities in italics from Bonferroni-corrected individual comparison.

4. Discussion

We provide evidence that urban birds incorporate cellulose from smoked cigarette butts into the nest and that this behaviour entails a reduction in the number of nest-dwelling ectoparasites. It appears that this effect may be due to the fact that mites are repelled by the nicotine, perhaps in conjunction with other substances, because thermal traps laced with cellulose from smoked butts attracted fewer ectoparasites than traps laced with non-smoked cellulose.
This novel behaviour observed in urban birds fulfils one of the three conditions necessary to be regarded as self-medication: it is detrimental to parasites [6]. However, to determine that this behaviour amounts to self-medication, it would be necessary to demonstrate that cigarette butts are deliberately collected and incorporated into nests because of their detrimental effect on parasites, and that such detrimental effect on parasites leads to an increase in host fitness.
The similarity between butt cellulose nest-lining and the use of green plant material in the nests of several species [711] suggests that the former may indeed be an urban manifestation of pre-existing behaviour, and it would be interesting to investigate whether HOSP and HOFI use green plant material in their nests (outside or within the cities). Alternatively, the use of cellulose from cigarette butts may be due to other properties of the cellulose (e.g. as a thermal insulator) unrelated to the effect of nicotine on ectoparasites. Presumably, both new and smoked butts can provide thermal insulation, but only the latter would protect against ectoparasites, thus a choice test under controlled conditions could be used to disentangle which is the primary function of this behaviour. Birds could distinguish smoked and non-smoked butts from their scent, just as some birds that use the chemical compounds of plants as defence against parasites appear to rely on olfaction to collect those with effective chemicals [24]. Thus, we propose that olfaction must be involved if the collection of cigarette butts by urban birds is a translation to the urban medium of a pre-existing adaptation against nest parasites.
Smoked cigarette butts contain a large number of toxic substances, including traces of pesticides [25]. Such pesticides, however, cannot explain why fewer mites were attracted to the thermal traps containing smoked butts, an effect that is consistent with nicotine being an arthropod repellent (figure 2). Nonetheless, those chemicals are in contact with the birds at the nest, and their toxicity could potentially counterbalance any benefits that may result from the reduction of ectoparasites occasioned by lining the nest with cigarette butts.


Vianey Palomera, M. Méndez-Janovitz, J. J. Zúñiga-Vega and E. Ávila-Luna helped in various parts of this project, constituting the BSc thesis of M.S.R. supervised by C.M.G.

Tibetans Evolved to Survive High Life, Study Says

Local people living there, carry unique versions of genes tied to blood oxygen levels.

Most Tibetans are genetically altered to life on the "roof of the world," according to a new study.
A Tibetan father and son on a pilgrimage around China's Mount Kailas.

The Tibetan Plateau (map) rises more than 13,000 feet (4,000 meters) above sea level. At such heights, most people are vulnerable to hypoxia, in which too little oxygen reaches body tissues, potentially leading to fatal lung or brain inflammation.
To survive the high life, many Tibetans carry unique versions of two genes associated with low blood hemoglobin levels, the researchers found.
Since hemoglobin is the oxygen-carrying component of red blood cells, the find might seem "really counterintuitive," said study leader Tatum Simonson at the University of Utah's Eccles Institute of Human Geneticsin Salt Lake City.
"Usually, if you or I or any nonadapted person went to high altitude, we would increase our hemoglobin levels to compensate for the low amount of oxygen."
But high hemoglobin levels have been linked to complications such as hypertension and chronic mountain sickness, Simonson said.
These negative effects could have led to a genetic mutation among Tibetans that "prevented them from making as much" hemoglobin, she noted.
Tibetan Genes Keys to Treating Height Sickness?
Previous research had found that Tibetans compensate for low oxygen levels by taking more breaths per minute than people living at sea level. In addition, Tibetans' blood vessels are wider, making them more efficient at delivering oxygen to body tissues.
Simonson and her colleagues searched for the genetic basis of high-altitude adaptations by collecting blood samples from villagers in Tibet living at 14,720 feet (4,486 meters) above sea level. (Get insider's tips on life in Lhasa, capital of China's Tibet Autonomous Region.)
The team then looked for patterns of genetic variation in the Tibetans' DNA and compared their findings to existing data on gene variation in lowland Chinese and Japanese populations, which are closely related to Tibetans.
Several variants of genes associated with high-altitude living, such as those that process oxygen, were found in Tibetans but not in their low-living neighbors. That includes the two genes that are strongly associated with low hemoglobin production.
Future research is aimed at teasing out more details about what exactly the altered genes do, which could help scientists find ways to "prevent people from getting sick" at high altitudes, Simonson said.

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