North American bird populations have declined by 3 billion - 30% - in the past 50 years. Cats are the number 1 killer. Number 2? Windows.
Hey friends -
In this week's letter:
Total read time: 11 minutes, 39 seconds.
After millions of years of evolution, our modern feathered dinosaurs have finally met their match. Over the past 50 years, North American bird populations declined by almost 3 billion individuals to just 7 billion remaining birds, a loss of roughly 30% of the population. Cats remain the primary killer with the over 150 million domestic and stray felines in the US responsible for between 1.3 and 4 billion bird deaths every year. Cats are and will remain a difficult problem to solve as most solutions are politically (and otherwise) unpalatable.
The #2 killer? Windows.
At first glance, you may not care much about birds. You may even be thinking of them as the nuance that excretes 1.3 million pounds of droppings on Canadian bridges. Birds nonetheless play hugely important roles in the healthy functioning of our ecosystems as insect eaters, pollinators, and seed spread-spreaders.
Insect-eating birds consume over 400 million tons of insects annually, in close competition with spiders as the primary predator keeping insect populations in check. The over 2,000 pollinating bird species are part of a core group alongside bats and bees that pollinate over 80% of flowering plants including 35% of our food crops. As seed-spreaders, birds distribute seeds huge distances from the parent plants ensuring that fruiting plants populations are not constrained by location-specific risks.
As we’ll find, preventing birds from crashing into windows is not a difficult or expensive problem to solve. It just requires a little understanding of how birds see glass and a whole lot of stickers.
Most birds are poorly designed to navigate windows. Death comes from collisions when flying full speed into the glass. Whereas humans are well equipped to deal with the complexities of this sometimes see-through, sometimes reflective material, most birds are disadvantaged.
The problems start with how birds understand glass. Birds neither perceive clear glass as a solid object nor can they differentiate between the reflection of an image in glass and the real thing. Their lack of understanding of glass is compounded by two physiological shortcomings - limited depth perception and poor contrast sensitivity. Limited depth perception is due to eye placement. Excepting birds of prey like eagles, most birds have eyes on the sides of their heads and wide fields of view to keep watch for predators. The tradeoff is that they have a limited field of view directly ahead and depth perception limited to the tip of their beak. Poor contrast sensitivity means that birds have difficulty differentiating between two adjacent objects with similar luminosity, which hinders their ability to detect dirt and dust on a window that might otherwise indicate that it is solid.
This combination of not comprehending glass as solid and physiological shortcomings leads to four problematic scenarios:
Most other animals have similar problems, they're just rarely traveling at speeds where collisions are problematic.
As we dig into the causes of bird collisions with glass, we find that the majority of deaths come from low-rises and individual homes. While each single-family home in the US is estimated to kill only a handful of birds each year, the sheer volume of homes leads to over 250 million bird deaths annually. As we'll discuss in a moment, low-rises combine many of the worst aspects of skyscrapers with the prevalence of single-family homes and lead to almost 340 million deaths a year. Skyscrapers come in a distant third at 500 thousand deaths per year but are nonetheless useful testing grounds for change.
The primary problem with single-family homes is their proximity to nature. Second only to total window area, the habitat immediately adjacent to windows is the best predictor of bird mortality. The vast majority of bird deaths occur during daylight hours. Throughout much of the day and when viewed from obtuse angles such as the ground beneath a bird feeder, windows are highly reflective of the environment around them. When they reflect trees and bushes, birds will often collide while attempting to fly "into" the environment.
When close proximity to nature is combined with large glass installations such as those on with low-rises (buildings 4-11 stories tall) and skyscrapers, we get rapidly increasing bird mortality. Whereas homes have a median mortality rate of 2.1 birds per structure, low-rises are 21.7 birds per structure, and skyscrapers 24.3. A 10% expanse in glass surface area leads to a 19-30% increase in bird death, and a 10% increase in tree height with close proximity to buildings leads to an additional 22-30% increase. These ranges included variability due to seasonable effects. The trend since the 1980s to build all-glass buildings that blend into surrounding vegetation has no doubt exacerbated these effects.
With such remarkably high numbers of collisions, it likely comes as little surprise that over 1/3rd of North American bird species have been identified in collisions. More species are likely impacted than have been identified due to sampling bias. Most studies have been done in northeast US cities during migratory seasons because the night-time light pollution from urban areas can mislead migratory birds to overnight in the area. Come morning, the birds find themselves surrounded by glass canyons leading to many deaths by collision. While helpful for researchers, it has meant that migratory birds that travel through the northeast are overrepresented in the actual counts of dead birds.
Thankfully collisions are relatively easy to prevent - make glass more visible to birds. It need not be all glass either, just glass installations below the tree line.
The obvious but unlikely to be realized solution is to use less glass generally. The environmental footprint of glass buildings goes beyond birds' lives - glass buildings are terribly energy inefficient. Glass is a poor insulator, which requires building with glass facades to spend outsized efforts to moderate internal temperatures.
Prominent awnings and overhangs provide visual clues for birds and reduce window reflections. Exterior grilles, shutters, and sunshades go a step further and ensure that there is something physical in front of the glass. For these to truly work, they must be on the outside of the window because they are of little help on the inside of the window design or viewing angle results in the glass reflecting the surrounding nature. The biggest challenges with these physical installations are that they tend to be expensive and, in my personal opinion, ugly.
A potentially promising development is glass with ultraviolet designs. Unlike humans, most birds see ultraviolet light. It has been hypothesized that this not only helps with sexual displays but also helps the birds navigate at night. More work has yet to be done to determine just how prevalent ultraviolet vision is across bird species before this becomes a viable option, as well as investigate how effective UV-glass may be early in the morning when ultraviolet light levels are low.
One of the most effective ways to stop birds from colliding with glass is also one of the cheapest - decals. Small high-contrast decals (e.g. dots) over windows below the tree-line can reduce over 90% of bird collisions. To make them work, we have to remember the physiological constraints we discussed earlier. The decals have to be spaced no more than 2 inches apart vertically and 4 inches apart horizontally to minimize the likelihood of birds attempting to dart through perceived passageways, much like they would in the forest, and high-contrast is necessary to overcome birds' naturally diminished contrast sensitivity. In case you were considering it - yes, birds of prey decals have already been tried. The other birds don't actually recognize the decals as birds of prey and simply fly into the windows around the decals. If they're placed as described above, a couple inches apart and high-contrast, they work well just like any other decal.
The Javits Convention Center in New York City is a prime example of the type of difference this can make. Before updates made in 2009, the building killed a bird every four days making it one of the most deadly buildings in the city for birds. The ground-level windows and windows surrounding the green roof were updated with patterns that are only minimally visible by humans and at a distance, yet give in-flight birds enough time to react and avoid a collision. The results have been an over 90% reduction in bird collisions and, together with other environmentally friendly changes like the aforementioned green roof, LEED Silver Certification for the entire building.
With relatively inexpensive and easy-to-implement solutions available, cities across North America are taking meaningful action to reduce bird collisions. Toronto was well ahead of the curve in 2010 and required bird-safe designs for all non-residential structures and any new residential buildings 4 stories or more high. Balancing implementation cost against anticipated effectiveness, the bird-safe windows only have to be applied to glass structures up to "mature tree height," about 40 feet off the ground.
San Francisco soon followed with their own ordinance in 2011 but, unlike Toronto who updated theirs in 2014 based on new research, San Francisco has not revisited theirs. Nearby Mountain View, California more recently required all new buildings, alterations, and additions to have bird-friendly facades for the first 60 vertical feet starting in 2017.
New York City is the largest and most impactful to take meaningful action, given both the city's size and positioning in paths of migratory birds. In 2015, Governor Andrew Cuomo began requiring state buildings to turn off non-essential outdoor lighting for nighttime hours during migratory seasons. Much more recently, Local Law 15 went into effect in January 2021 which requires all new buildings to use a minimum of 90% bird-friendly materials in the first 75 feet above the ground.
Chicago is also among the recent major US cities to enact meaningful legislation. Millions of birds pass through the city each year on their migratory paths to Lake Michigan and beyond. Chicago requires buildings to meet environmental guidelines per a Sustainability Development Policy initial passed in 2004. A 2020 ordinance updates the qualification to increase emphasis on bird-safe design, recognizing both buildings that make baseline improvements and those that meet enhanced standards as forth by LEED, the most widely used green building rating system in the world.
At this point, you're probably wondering if "bird-friendly" means you can just get by with a "we love birds!" banner on the front of the building. The short answer is no, and the longer answer is that LEED has a formula for determining bird-friendliness. The full details are rather complex, but the basics are relatively straightforward. Each material to be used on a facade is given a threat score - opaque materials like concrete get a 0 and fully see-through materials like clear glass get a 100. An overall threat score is calculated based on the weighted average threat score sums of the materials used, their surface area, and vertical location. Each city can enforce its own standards and still use LEED's threat score calculations to enforce local regulations. LEED itself requires that buildings achieve a Bird Collision Threat Rating of 15 or less if they want to receive the bird-friendly credit as part of an overall LEED certification.
New regulatory regimes are often opportunities for entirely new industries to emerge and bird-friendly laws are no exception. Lawyers are likely to find new bases for environmental cases under the recently enacted bird-friendly laws. The first of these came to light in 2013 when an Ontario court found a developer responsible for hundreds of birds' deaths in violation of the Ontario Environmental Protection Act. We're likely to see similar cases on the horizon in New York and elsewhere.
New consulting, manufacturing, installation, and auditing businesses will launch to enable glass decals and bird-friendly glass production. New building developers will need to engage with environmental consultants during the design process to understand and eventually quantify the high-risk aspects of a project. When sourcing materials, the developers will need to identify and engage new vendors who can supply materials with appropriate threat factors. Those vendors will in turn engage the new manufacturers who produce threat-factor-certified materials. The design process will likely be iterative as the building evolves and facade materials are updated. For those pursuing LEED certification, building design will also include plans for how to monitor the building for collisions so that updates can be made as needed.
Once the building is spec'd, specialists will be needed to install many of the new materials that help prevent collisions- grates, decals, special ultraviolet glass. Once installed, third-party auditors will need to certify that the facade has been installed as per the design and does not exceed the proscribed threat rating.
There will be inevitable missteps likely play out over years and decades as the relatively new regulations are implemented. Scaffolding in New York City is an ongoing example of how similarly well-intentioned regulations can lead to unintended consequences over time. In 1980, New York passed a law requiring the facade of all buildings 6 stories and taller to be inspected by an engineer every 5 years. Cheap developers found a loophole - there are no restrictions on how long scaffolding can be in place and no time frame over which crumbling facades must actually be fixed as long as the scaffolding remains erect. It can be orders of magnitude cheaper to keep the scaffolding up indefinitely and not fix the facade at all than to actually make the necessary repairs. With such perverse incentives, the regulations have inevitably led to lots of unnecessary scaffolding erected for years on end while building facades crumble behind them. While the original facade inspection law was well-intentioned, expensive unintended consequences, including lost sales by small businesses whose patrons pass them as they wither under neighbor's overhanging scaffolding, beg for revised legislation.
We don't yet know what the unintended consequences will be from the new bird-friendly ordinances, but trust that beyond the trivial lawsuits that seem to be an inevitability in the US we will find both enterprising individuals who cut corners as well as negative externalities born by the communities surrounding these new buildings. These aren't reasons to avoid or halt new well-intentioned regulation, but rather an opportunity to look for inspiration on how such effects can be mitigated. From a legislative viewpoint, we can look to Toronto. In 2014, the Canadian city updated the original 2010 bird-friendly legislation to reflect new understandings of how to effect bird collision reductions without as many tradeoffs.
From a private sector perspective, we can look again to Javits Center in New York. The 3.3 million square foot convention center built a 7-acre green roof alongside their bird-friendly window updates. While the Javits Center was not initially designed or built with environmental concerns in mind, the economic benefits of environmentally friendly updates have since established a compelling business case on which to pursue such projects. The green-roof and surrounding bird-friendly glass is not only home to 29 bird species, 5 bat species, and thousands of honeybees, it also reduced the building's energy use by 26%. The project is a crown jewel in a larger energy reduction program that reduced total building energy use by 35% in the first three years, saving the building over $2 million. The energy savings was part one of a two part business case. Javits was also able to able claim federal and municipal tax exemptions both for the overall energy reductions and achieving LEED Silver certification.
We have a very real challenge to reverse bird population declines. We know how to reduce bird-glass collisions, the #2 killer of birds - it is as simple as decals over windows on the bottom 4 stories of buildings. There will be costs born by developers and passed on to building occupants to support the new industries required to effect and audit bird-friendly glass. Given the barriers to entry, these products and services are likely to become commoditized over time leading to only minimal costs that pale in comparison to the effects of collapsing bird populations. We'll inevitably make mistakes with our initial regulations, but we have no lack of successful examples of how to revise legislation and update incentives to promote the beneficial behaviors we intended, if only we have the same will to do so that drove the regulations in the first place.
More tiki drinks for the hot weather! And this one is t(r)opical.
1.5oz Dark Rum
0.75oz Campari
2oz Pineapple Juice
0.5oz Lime Juice
0.5oz Coconut Sugar Syrup
Pour everything into a shaker. (Coconut sugar syrup is just 50/50 coconut sugar to water. Light brown or standard white sugar will work in a pinch). Fill with ice until the liquid is covered. Shake for 20+ seconds, until the outside of the shaker is nice and frosty. Fill a rocks glass (or tiki mug!) with ice. Strain the drink into the rocks glass and enjoy.
I love making cocktails with pineapple. Shaking pineapple juice always produces this thick foam on the top that gives you a great mustache. I can’t think of too many other drinks that combine the deep molasses of a dark rum with the sweet bitterness of Campari. The coconut sugar plays up the rum notes, but you could equally well swap the coconut for oleo saccharum (a fancy name for sugar that’s had citrus peels sitting in it) and up the lime juice to give this more of a bitter-sour seaside vibe. However you enjoy it, it’ll be great.
Cheers,
Jared
