Rest in peace, little pigeon!

It was a typical Tuesday afternoon when an ominous loud thud from the windows interrupted our professor’s passionate lecture. A feather was left stuck on the glass panel, with suspicious blood stains dotting the glass. I spun around and saw faces of horror and trauma – they had all, unfortunately, witnessed the full speed collision of an unsuspecting bird into the window.

Victim of the bird-building collision, a male Pink Neck Green Pigeon
Photo by Lim Chun Wei

A few weeks ago, in the same room, we learnt that bird-building collision (also known as window strike) is not a rare occurrence in cities. In the United States alone, an estimated 97.6 to 975.6 million birds die each year from window strikes (Klem, 1990). The worldwide death toll is estimated to be in the billions (Klem, 2008)! Singapore, however, does not have a comprehensive study on this issue. To change things up, the Bird Group embarked on a five-year study of migratory bird collisions in Singapore. Their preliminary data documented a total of 47 window strike between September 2014 and April 2015, with 20 in the central business district (Low, 2015).

Reasons for window strikes

So why do birds crash into windows? Can’t they see the glass? Well surprisingly (or not), windows are invisible to them (Klem, 1989). Birds usually cannot differentiate between reflections and real vegetation. They collide into window panes when flying through vegetation in urban areas, either by trying to reach the reflected greenery or attempting to fly through the corridors to vegetation on the other side (Klem, 2006). In some cases, a territorial bird sees its own reflection as a rival and launches repeated attacks on the window pane (Klem, 2006). Lastly, some migratory birds use celestial patterns to find their way at night. Artificial lights from buildings confuse them, thus attracting these birds to their doom (Low, 2015). On an unrelated note, Singapore actually tops the list as one of the world’s worst light polluted country (Falchi et al., 2016).

Perhaps our lights are a bit too bright?
Photo by Rodney Topor
(Image from:

Contrary to popular belief, most victims of window strikes die not from a broken neck, but instead, due to intracranial haemorrhage. A head on collision ruptures the blood-brain barrier, leading to sub-dural bleeding and brain damage (Klem, 1990a). The most observable external injury is usually a broken beak. And not all birds die from the collision. Some may be stunned or unconscious but then fly off once they recover. Others may merely be startled and fly off immediately (Klem, 1990a).

Ways to prevent window strikes

Over the past few years, many have poured in efforts in search for ways to prevent possible bird-building collision. Here are some of the commonly used methods to counter the window strike problem:

  1. Use of Window Patterns

A relatively simple way to counter window strikes would be to put patterns on the glass, so that the birds can see the windows. In the video below, Christine Sheppard, Collisions Program Manager for the American Bird Conservancy, has being working with her research team to find the most effective window patterns to prevent window collisions.

(Source: YouTube)

Their experimental results show that most birds avoid flying through a horizontal spacing of less than 2 inches (~5cm) or vertical spacing of less than 4 inches (~10cm). Therefore, decal patterns placed uniformly on the window pane or tape strips can be placed to prevent window strikes. UV stickers that are invisible to our eyes but visible to the birds can also be used to maintain the aesthetic of a “clear” glass (Cornell Lab, 2009). In any case, patterns must be on the outside of the window (facing the birds) for it to be effective.

  1. External window accessories

Do you have problems with birds hitting your windows but don’t want to change your window glass or tediously apply decals? Window screens could be your answer! Small-mesh netting or window screening can be placed outside a window, at least 3 inches away from the glass. If the netting is taut enough, birds can bounce off before colliding with the actual glass. External shutters or sun shade can also be used to block the reflection of the glass, making the window entirely opaque when it is not in use (Cornell Lab, 2009).

Bird screen used on window
(Image from:

  1. Switching off unused lights at night

(Source: YouTube)

For tall commercial buildings, like in the Central Business District, you should consider turning off the lights at night. I understand that a lit up building may create a pretty night-time skyline, but this video above may persuade you otherwise. It discusses reasons why birds might prefer to fly at night and how they are attracted to light sources in buildings (Soh, 2014). One campaign to switch off lights in Chicago resulted in an 80% drop in mortality due to bird-building collisions show how effective this strategy can be. Aside from saving birds’ lives, you get to save on electricity too. So it’s a win-win situation for you!

  1. Relocating bird feeders

For bird lovers who have bird feeders at home, you may want to reconsider their placements. If you would like to place the bird feeder nearer to your home, you should keep it within 0.9m from your window (Cornell Lab, 2009). Anything beyond that, the speed they gathered when taking flight from the feeder to the window can result in a fatal impact. For those who are uncomfortable with a bird feeder so near to home, you can alternatively, place your feeder at least 9m away from your windows (Cornell Lab, 2009). This would then ensure that birds will not associate them as possible habitats when they fly off from the feeder. Don’t let your love for birds be the cause of their death!

Final thoughts

Ever run into glass doors because you were not looking? You may have ended up with a bruised nose but to birds, glass can be fatal. Birds are not just simply pretty to look at, they also play important ecological roles. Birds are great seed dispersers and pollinators. So when the bird populations decline, reproduction rates of many plants also decrease too (Tabur & Ayyaz, 2010). Recognising the importance of birds, cities like Toronto, Chicago and New York City have put in place policies and guidelines to mitigate the bird-building collisions problem. Perhaps it’s about time for Building and Construction Authority (BCA) to look into updating its building regulations too?



Cornell Lab. (2009). Why Birds Hit Windows—And How You Can Help Prevent It. Retrieved from

Falchi, F., Cinzano, P., Duriscoe, D., Kyba, C. C., Elvidge, C. D., Baugh, K., & Furgoni, R. (2016). The new world atlas of artificial night sky brightness. Science advances2(6), e1600377.

Klem, D. Jr. (1990). Collisions between birds and windows: mortality and prevention. Journal of Field Ornithology 61:120–128.

Klem, D. Jr. (1990a). Bird Injuries, Cause of Death, and Recuperation from Collisions with Windows. Journal of Field Ornithology 61 (1): 115-19

Klem, D. Jr. (2008). Avian mortality at windows: the second largest human source of bird mortality on Earth. Tundra to tropics: connecting birds, habitats and people.

Klem, D. Jr. (2006). Glass: a deadly conservation issue for birds. Bird Observer34(2), 73-81.

Low, A. (2015). Migratory Bird Collisions in Singapore. Singapore Bird Group. Retrieved from

Loh, J. (2014). Lights Out Effort Reduces Deadly Bird-Building Collisions. VOA News. Retrieved from

Tabur, M. A., & Ayvaz, Y. (2010). Ecological importance of birds.

Marine life in an urban environment

Marine life in an urban environment

by Crystle Wee

When we think about urban environments, we often fail to notice that our marine environments are just as, if not more, influenced by human development. While the focus in urban ecology has been largely dominated by discussions of terrestrial or freshwater environments, it is also vital to think of how urban development shapes marine ecosystems and habitats.

One of the key ways in which marine environments are degraded in Singapore is through widespread land reclamation and the alteration of our natural coastlines by constructed seawalls. After reclamation work is carried out, the area can be more prone to problems such as soil erosion, and this makes it necessary to build more infrastructure to reinforce coastal stability and mitigate erosion. Did you know that around 63% of Singapore’s coastlines are covered by seawalls? We need the seawalls to dissipate the energy in waves so it does not wear away our beaches and coastal areas. But seawalls are very harsh environments that may not support biodiversity the way natural coastal ecosystems do.  Here’s a short infographic I created on land reclamation, which is what I feel is the biggest challenge to marine life in our coastal waters.

Look at changes in reclamation and development of our coastal areas from the 1950s to 2002. Since then, even more reclamation work has been completed, so much so that most of our coastal environments are different from what they were before (Images courtesy of Ria Tan, WildSingapore)


Marine biodiversity that persists despite the pressures of development

Reclamation and development have caused high rates of sedimentation and hence, very turbid waters and Singapore has lost more than 60% of its coral reefs. Nevertheless, Singapore still has an impressive array of marine life: at least 50 sea anemone species, 12 seagrass species and around 255 species of hard corals (Hilton & Manning, 1995; Chou, 2006; Huang et al., 2009). To put that in perspective, we have around a quarter of all hard coral species that can be found in the world!

 Here are pictures of corals I’ve taken in Singapore’s waters! Pretty beautiful right?


Solutions to increase biodiversity in affected areas

The Experimental Marine Ecology Lab in NUS, led by Prof. Peter Todd, is researching methods to increase biodiversity along these sea walls by trying concrete tiles with different complex designs. Depending on the type of surface, the tiles can provide different ecological niches and spaces for a variety of marine organisms to colonise. I like this analogy…imagine a hawker centre in Singapore that only serves chicken rice. Now imagine a similar hawker centre, except this one also serves laksa, satay, roti prata and fishball noodles too! Which one do you think will attract more people? I know I’d definitely prefer the one with more variety! In a similar way, a marine environment with a variety of habitats will attract organisms with different habitat preferences. And so tiles with a greater variety of spaces, are more likely to provide suitable homes for a mixture of different organisms.

These concrete tiles can be a more favourable environment for marine snails and other organisms that typically live in rocky shore habitats. (Images courtesy of the Experimental Marine Ecology Lab, NUS)


If we want to better understand how human processes shape changes in the ecology and function of marine communities, then we need to focus more attention on urban ecology in marine environments. With more studies, hopefully we can think up better ways to develop sustainably and better consider the marine life we share our home with.



Chou L.M. (2006). “Marine habitats in one of the world’s busiest harbours,” in The Environment in Pacific Harbours, E. Wolanski, Ed. Dordrecht: Springer, 2006, ch. 22, pp. 377-391. 

Hilton MJ and S. S. Manning, “Conversion of coastal habitats in Singapore: indications of unsustainable development,” Environmental Conservation, vol. 22, pp. 307-322, 1995.

Huang, D., Tun, K. P., Chou, L. M., & Todd, P. A. (2009). An inventory of zooxanthellate scleractinian corals in Singapore, including 33 new records. Raffles Bulletin of Zoology, 22, 69-80. 

Loke LHL, Todd PA. “Structural complexity and component type increase intertidal biodiversity independently of area.” Ecology. 97 (2016) 383-393.

Loke LHL, Liao L, Bouma TJ, Todd PA. “Succession of seawall algal communities on artificial substrates.” Raffles Bulletin of Zoology. 32 (2016) 1-10.

Loke LHL, Ladle RJ, Bouma TJ, Todd PA. “Creating complex habitats for restoration and reconciliation.” Ecological Engineering. 77 (2015) 307-313.

Loke LHL, Jachowski NR, Bouma TJ, Ladle RJ, Todd PA. “Complexity for artificial substrates (CASU): software for creating and visualising habitat complexity.” PLoS ONE (2014) e87990.

Tan, R. (2008). “Loss of coastal ecosystems” Retrieved April 2017.


Nature Ways

We’ve all heard and talked about Singapore’s nature reserves, nature parks and park connectors. But what about nature ways? I asked three of my BES friends recently and none knew what they are. Alas, these important but rather inconspicuous green corridors have rarely been given a mention: there isn’t even a sign to inform people that they are walking along one! Another reason for their low profile may be their scarcity: there are just 16 in total spanning a relatively short total distance of 68 km (Fig. 1.). Compare that to Singapore’s 78 park connectors totalling 300 km in length (Abdullah, 2015)!

So…what is a nature way?

Just by looking at Fig. 1, the nature ways resemble park connectors but they couldn’t be more different! Many park connectors meander through housing estates and are equipped with user-friendly facilities, such as benches, shelters, cycling tracks and even exercise corners. However, most nature ways are more like enhanced roadside streetscapes (they run alongside roads) and they lack user facilities. Additionally, unlike most park connectors (or nearly anywhere else for that matter) which are planted with trees of the same species and at uniform heights (urban monocultures) to present a “neater” and “orderly” image, nature ways are intentionally planted with a wide variety of plant species and have a more layered vegetation structure to mimic a forest as closely as possible (NParks, n.d.-a) (Fig. 2).

Fig. 1. Map of all the nature ways in Singapore.

Fig. 2. Vegetation structure of a nature way.

Function and importance of nature ways

Why develop nature ways? Well, nature ways are important as they help restore ecological connectivity between fragmented green patches in highly urbanised Singapore. By more closely replicating natural forests, nature ways attract a variety of animals that use them as habitats and wildlife crossings. Animals including birds, reptiles, amphibians, and invertebrates (that occupy different layers) are thus, able to move between green spaces of high biodiversity (NParks, n.d.-a). This facilitates gene flow and dispersal of animals, which are important to reduce inbreeding in otherwise isolated population (Angold et al., 2006).

For example, the longest one, Tengah nature way (TNW), links Bukit Timah Nature Reserve, Central Catchment Nature Reserve and the Western Catchment (NParks, n.d.-b). Surveys conducted to assess its effectiveness found forest-edge species, such as the horsfield’s baron butterfly and common gliding lizard, which were rarely seen before at that location (Chua, 2015), suggesting that the TNW was attracting more animals and facilitating their crossings.

Are there areas for improvement in terms of the design and development of nature ways?

Though nature ways are developed with well-intentions, I feel that there are areas which can be improved. Some of the nature ways (especially long ones like TNW) are not continuous, but occasionally separated by artificial barriers, such as road junctions. This could hinder the movement of animals that are road-phobic and would avoid crossing even the narrowest of roads. Indeed, numerous studies have documented road avoidance behaviour or reluctance to live close to the roads in many animal species, including birds, insects, and mammals (Laurance et al., 2009; Muñoz et al., 2015). Even if the animal does decide to cross the road, it would have to face an onslaught of vehicle traffic and risk being hit by one, which could lead to road mortality. Therefore, it would be better if nature ways could avoid road crossings altogether, but I can only assume that because nature ways should link one green space to another, NParks would have already planned the configuration of nature ways to minimise road crossings.

Additionally, vegetation in some parts of the nature ways is sparse and often sandwiched between the road (some of which have heavy traffic) and pedestrian path (Figs. 3 and 4). This could influence the abiotic conditions in nature ways, resulting in warmer and drier microhabitats as compared to forests because of greater exposure and proximity to impervious surfaces. Noise (vehicles and pedestrians), light (from public street lighting) and air pollution (vehicular emissions and dust) will also reduce the quality of these roadside habitats. Therefore, different environmental conditions compared to natural habitats could deter some species from using the nature ways as crossings or habitats. To reduce these effects, more plants should be planted especially in vegetation-sparse areas to increase vegetation density and improve the quality of re-created habitats along nature ways.

Fig. 3. Portion of the Tengah Nature Way at Bukit Batok Ave 2. Credit: Estella Tan


Fig. 4. Portion of the Chua Chu Kang Nature Way at Teck Whye Ave. Credit: Estella Tan

Finally, I came across a paper by Jain et al. (2014) which argue that the existing method of merely planting bird- and butterfly-attracting species capable of withstanding roadside conditions is inadequate. Instead, planners should also consider the ecological needs of species found in the source and sink fragments before deciding on the types of flora to plant along nature ways (Jain et al., 2014). I concur with the authors, as based on my experience walking along the nature ways, I seldom see a great variety of fauna, and one reason could be the incompatibility of plant species to the fauna found in the connected habitat patches, which deters them from using the nature ways.

Final thoughts

Overall, I am all for the development of nature ways as a habitat de-fragmentation strategy to connect various urban green spaces and conserve Singapore’s biodiversity. The good news is that NParks aims to increase the total length of nature ways to 180 km by 2030 (NParks, n.d.-a)! I do hope that they consider the areas for improvement (as mentioned above) during the development of new nature ways in the future. Also, wouldn’t it be great if park connectors (and other green strips) also adopted the layered vegetation structure and are lined with a wider variety of plant species? That could attract even more wildlife and, in so doing, foster closer connections between people and nature in an urban environment. Finally, I could find very few publicly-available research papers or data on the effectiveness of nature ways, with suggestions for improvement. Perhaps NParks conducts its own internal evaluations, but I do see a lot more room for study (ps. potential FYP topic for anyone who’s interested!).


Abdullah, Z. (2015, September 21). Singapore park connectors reach 300km at 25-year mark. The Straits Times. Retrieved from

Angold, P. G. et al (2006). Biodiversity in urban habitat patches. Science of the Total environment, 360(1), 196-204.

Chua, G. (2015, January 23). How Singapore makes biodiversity an important part of urban life. Citiscope. Retrieved from

Jain, A. et al (2014). Moving away from paper corridors in Southeast Asia. Conservation Biology, 28(4), 889-891.

Laurance, W. F. et al (2009). Impacts of roads and linear clearings on tropical forests. Trends in Ecology & Evolution, 24(12), 659-669.

Muñoz, P. T. et al (2015). Effects of roads on insects: a review. Biodiversity and conservation, 24(3), 659-682.

National Parks Board (NParks). (n.d.-a). Nature Ways. Retrieved from

National Parks Board (NParks). (n.d.-b). Singapore’s longest green corridor will enhance biodiversity in the South West District. Retrieved from

The Singapore Index (SI)

Over the last 30 years, the world’s urban population has been rapidly increasing and is forecasted to reach nearly 5 billion by 2030 (Seto et al., 2012). This has been accompanied by rapid urban land expansion, which is occurring on average twice as fast as urban population growth (Seto et al., 2012). Therefore, if current urban population growth rates remain unchanged, urban land cover is expected to triple in size by 2030 (Seto et al., 2012). This increase would exacerbate biodiversity loss due to even more habitat fragmentation and altered local climates, among other things. However, cities still support some species and can make efforts to conserve them. How then, should cities protect urban biodiversity and ensure their efforts are making progress? Thinking along those lines, I recalled reading a publication by the Centre for Liveable Cities (CLC) (where I used to intern) that discussed biodiversity conservation efforts in cities. Two words caught my attention: “Singapore Index”.

What is the Singapore Index (SI)?

No, this is not about Singapore’s financial stock market. Instead, it involves taking stock of biodiversity in cities. As the name suggests, the SI (also known as City Biodiversity Index) was conceived in Singapore! First proposed at the Conference of Parties (COP) to the Convention of Biological Diversity (CBD) in 2008, the SI is a self-assessment tool with a scoring system for cities to measure and evaluate their progress in biodiversity conservation by comparing with a baseline year (Chan et al., 2014). In 2010, the SI was formally endorsed by the COP (Kohsaka et al., 2013). With the SI, cities can benchmark their progress in reducing the rate of biodiversity loss in urban environments, measure their ecological footprints and identify gaps in biodiversity information (Rodricks, 2010).

In short, it consists of two components (Chan et al., 2014):

  • “Profile of the City” which includes background information of the city
  • 23 indicators in three categories: (1) native biodiversity in the city; (2) ecosystem services provided by biodiversity in the city; and (3) governance and management of biodiversity in the city.

To know more about the SI and indicators used, you can read the user’s manual here! However, if reading a lengthy document doesn’t appeal to you (I totally understand), check out these two videos (will embed), where Dr Lena Chan, Director of the National Biodiversity Centre (NBC) under the National Parks Board, explains how the SI works and why it is useful:

Implementation of the SI

Unsurprisingly, Singapore was one of the first to implement the SI. How did Singapore fare? Not too bad! She scored well in governance, but could improve in terms of ecosystem services and freshwater supplies (Tok, 2011). Other cities have also implemented the SI, including 14 in Japan, India’s Mira Bhainder and Canada’s Edmonton (Kohsaka et al., 2013). However, there were some challenges when it came to implementation. After all, no two cities are exactly alike. Challenges include no clear definition of what defines a “natural area” and “fragmentation”, lack of data on native and invasive species, and difficulties in (1) calculating ecosystem services and (2) determining how much budget to allocate to general environmental causes and biodiversity-specific activities (Kohsaka et al., 2013).

For example, Yokohama is Japan’s second-largest city, making regular comprehensive surveys of biodiversity and terrestrial ecosystems difficult to conduct and seen as unrealistic due to budget constraints (Kohsaka et al., 2013). Indeed, lack of biodiversity data and financial constraints are major challenges in applying the SI especially for cities in developing countries. Even Edmonton, Alberta, Canada, received a relatively low biodiversity and ecosystem services score (Kohsaka et al., 2013). However, one must consider the climate (Edmonton is cold!). This is a reminder that caution should be exercised when comparing scores across cities.

Final thoughts

Overall, despite inevitable compatibility issues with the SI, I feel that it is still a useful tool. Cities may choose to add indicators to the SI or even be inspired to create their own indices to best suit their contexts. Ultimately, the main takeaway is that there is no “one size fits all” index, because it is nearly impossible to include indicators that all cities will have data on. Make it too broad, and the SI will lack depth. Make it too specific or rigid, and it will lack flexibility and applicability. At least the SI recognises the importance of biodiversity in urban environments and spurs cities to keep track of their conservation efforts, a crucial element in the pursuit of sustainable urban development.


Chan, L. et al (2014). User’s Manual on the Singapore Index on Cities’ Biodiversity (also known as the City Biodiversity Index). Singapore: National Parks Board, Singapore.

Kohsaka, R. et al (2013). Indicators for management of urban biodiversity and ecosystem services: city biodiversity index. In Urbanization, biodiversity and ecosystem services: challenges and opportunities (pp. 699-718). Springer Netherlands.

Rodricks, S. (2010). Singapore City Biodiversity Index. Retrieved from

Seto, K. C. et al (2012). Global forecasts of urban expansion to 2030 and direct impacts on biodiversity and carbon pools. Proceedings of the National Academy of Sciences, 109(40), 16083-16088.

Tok, C. (2011). City Biodiversity Index. Retrieved from