Killer hummingbirds revisited

sherlock-holmes

“It’s a photo of a dead hummingbird! What do you make of it Holmes?”
“Impossible to say without additional evidence, Watson.”

Periodically over the nearly nine years since the publication of Killer hummingbirds?, I’ve received comments from people taking issue with what they believe that post says. Typically, these readers have witnessed an attack by one or more hummingbirds on another and wish to inform me that I’m wrong to say that hummingbirds never kill each other. The first problem is that I didn’t say “never,” and they would know this had they read as far as the bold black text in the middle of the post:

 “Only birds weakened by hunger, disease, or injuries… are vulnerable to injury and, in rare instances, death from other hummingbirds…”

Some of the reports clearly fit the qualification above, because, to quote more of the original post:

a healthy hummingbird will either defend itself or flee before a more aggressive individual gets the chance to do any significant damage.

Others provide few if any useful details of the event, even when prompted, and still others are just accounts of finding a dead hummingbird and assuming, because they had previously observed combat, that it was a case of trochilicide.

This brings us to the other problem with these reports, which is that they are never accompanied by any objective evidence—photos or video—that would support their accounts of the events (much like reports of yellow hummingbirds). A recent correspondent claimed to have seen a Black-chinned Hummingbird…

“…physically stick his bill deeply into another h.bird’s belly, twice! Then 2 more times into the back of the others neck.”

There are a couple of problems with this description as evidence of hummingbirds fighting to the death, even if one combatant is severely disadvantaged. The first is that poking is rather common in hummingbird combat, and the disappearance of the tip of an aggressor’s bill into the thick plumage of the “victim” would be understandably alarming to someone unfamiliar with hummingbird anatomy.

BCHU-bouf-brain

A hummingbird poking another’s body with its bill is a bit like someone poking Marie Antoinette in the bouffant with a knitting needle.

The second is that, even when the bill passes completely through the feathers and makes contact with the other bird’s body, hummingbird anatomy makes a fatal penetrating wound highly unlikely except in freak circumstances (see page 23 of A Field Guide to Hummingbirds of North America for an example).

This X-ray CT image of a Ruby-throated Hummingbird, showing its huge, deeply muscled rib cage, short skin-and-bones neck, and virtually nonexistent “belly,” demonstrates why hummingbirds are not as vulnerable to penetrating wounds as humans are (or as capable of inflicting them):

CT scan of a Ruby-throated Hummingbird. Copyright Digimorph.org

CT scan of a Ruby-throated Hummingbird. Copyright Digimorph.org

The issue of hummingbirds injuring one another in combat took a fascinating twist in 2014, when Alejandro Rico-Guevara of the University of Connecticut and and Marcelo Araya-Salas of New Mexico State University announced their discovery that the unusual bill shapes of adult male Long-billed Hermits make them more effective at inflicting potentially painful puncture wounds than the bills of females and juvenile males, and that males with longer, pointier bill tips were more successful at defending territories.

These revelations were newsworthy precisely because the bill shapes of the vast majority of hummingbird species, including all of the familiar North American species, show no such adaptations and confer no apparent advantages in combat. It’s also noteworthy that while the researchers observed male Long-billed Hermits poking each other during combat, they did not mention observing any serious injuries, much less fatal ones, resulting from these interactions. In fact, most of the “fighting” shown in their video consists of belligerent posturing and vocalizing with little physical contact, similar to the combat behavior of most North American hummingbirds:

(Note that the black-and-white segment depicts two non-hermit species, and the last sequence depicts courtship and mating, not fighting.)

So now we have compelling evidence that males of at least one hummingbird species have bills adapted for use as “stabbing” weapons, yet documentation of fatal encounters between healthy, normal hummingbirds is still almost as elusive as Bigfoot. I expect it will remain so, but I’m open to persuasive evidence.
Decreux LikenessesResources:

Rico-Guevara, Alejandro, and Marcelo Araya-Salasb , 2014. Bills as daggers? A test for sexually dimorphic weapons in a lekking hummingbird. Behavioral Ecology 26(1): 21-29.

Digimorph.org: Archilochus colubris, Ruby-throated Hummingbird by Dr. Ronald Stearman, The University of Texas at Austin.

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New post at my Web site

WN-Jacobin

I’m such a bad blogger. I didn’t even post about my spectacular trip to Trinidad and Tobago last summer where I photographed this stunning White-necked Jacobin.

Has it really been almost a year since I last posted here? I’m still working on the second edition of A Field Guide to Hummingbirds of North America, so I haven’t been doing much writing otherwise, but I did just add a post to the News tab on my Web site about a controversy that erupted during the spring 2012 Ruby-throated Hummingbird migration. Hope you enjoy it!

P.S.: If you’d like to see more of my photos from Trinidad and Tobago, check out the album on Flickr.

“Chemical-free” sugar?

My reply to the following e-mail bounced, so I’ll answer it here:

I’ve read the first part of your article on hummingbirds about what  to make when you feed them.

Before reading the article, I just made hummingbird food with organic sugar. I am concerned about the addictive and other chemicals in white sugar. Is there any white sugar available on the market that does not contain chemicals?  or a way to transform organic sugar in white?

Thank you for your time.

In the strictest sense, there is no product of any kind on the market that doesn’t contain chemicals. I’ll need to know what specific substances you’re concerned about (other than iron) before I can answer your question, but the way it’s phrased suggests that you may have fallen victim to fear-mongering hyperbole about white sugar. In that case, this post may be helpful:

Search of the Week: “if refined sugar is so bad for us then why do we feed it to hummingbirds??”

One feederful of organic sugar isn’t going to kill hummingbirds because the iron concentration is very low. It’s chronic exposure to excess iron over weeks, months, or years that may cause illness and death. Unfortunately, there is no simple home remedy for removing the residual iron from organic/”raw”/turbinado sugar.

Search of the Week: “hummingbirds won’t eat instant nectar”

Lucifer Hummingbird female

All of Arizona’s famous feeding stations use plain sugar water to attract avian celebrities such as Lucifer (above, female), Magnificent, White-eared, and Violet-crowned hummingbirds. (photo © Sheri L. Williamson)

Maybe they’re trying to tell you something. Most of the “instant nectar” and “hummingbird food” products on the market are adulterated with petroleum-based artificial dyes and/or preservatives, so it’s safer if the birds don’t eat them.*

Even products that claim to contain natural coloring aren’t necessarily trustworthy. On a recent visit to one of the big-box pet stores, I encountered three versions of a brand of “instant nectar” touted on the Web as containing “natural red coloring.” The ingredient list showed that the concentrate and one of the two powders contained FD&C Red No. 40, which has been found to cause harm in laboratory animals at dosages substantially lower than a hummingbird would be exposed to by drinking one of these products. The label on the other powder listed beet coloring, which may not be the best choice of natural coloring for hummingbirds for reasons I explained in an earlier post.


* The few “instant nectar” products that don’t contain unnecessary and potentially harmful additives may not hurt the birds, but they’ll put an unnecessary dent in your bank balance. They’re ≥99% sugar priced at five to ten times what you’d pay for white granulated sugar at the grocery store. What you’re really paying for is the colorful, “convenient” package, not a better product. If you’ve got cash to burn, try superfine or caster sugar, which dissolves more quickly in cold water than regular granulated. Organic sugar, “raw” sugar, and “evaporated cane juice” are other pricey alternatives that might seem worth the extra green, but their beige to brown color indicates the presence of iron, which is known to be a potentially deadly problem for hummingbirds. Until we know more about how much supplemental iron hummingbirds can tolerate, they’re not worth the risk.

Review: Feeder Fresh Nectar Defender

(Originally submitted at Duncraft, which I do not patronize because it sells various overpriced “nectar” products that contain artificial dyes, preservatives, and/or other potentially harmful additives that don’t belong in hummingbird feeders.)

A bad idea

1out of 5

The active ingredient in this product is reportedly copper, which is an essential micro-nutrient at natural (low) intake levels and a potentially toxic heavy metal at higher doses. The fact that copper accumulates in birds’ bodies combined with hummingbirds’ extreme appetites increases the risk that the copper in this product will accumulate over time to levels that may cause scientifically documented problems such as behavioral changes, developmental abnormalities, reduced egg production and nestling survival, etc. That’s a pretty high price to pay for reducing feeder maintenance.

Search of the week: “how do i know if the hummingbirds are to fat”

When they can’t get off the ground.

Image

To survive their epic migrations, Rufous Hummingbirds may double their body weight by converting energy-rich sugar into energy-rich fat.

Seriously, a wild, free-living hummingbird can’t get too fat. Fat is fuel for migration, and they pack on the grams as necessary to prepare for travel and shed them just as quickly when the journey is over.

Beware the wrath of the birding legions!

A Snowy Owl at Benton Lake National Wildlife Refuge in Montana, safe from murderous bureaucrats and and Silver-bellied Gashawks.

A Snowy Owl at Benton Lake National Wildlife Refuge in Montana,
safe from murderous bureaucrats and and Silver-bellied Gashawks.
CC image courtesy of USFWS Mountain-Prairie on Flickr.

(Title borrowed from a column by the late, great Molly Ivins.)

On Monday morning, the New York Daily News broke a story about the Port Authority killing Snowy Owls at airports in New York City. Follow-up articles contrasted trigger-happy NYC with the more responsible and humane policies of Boston’s Logan Airport (a famous location for wintering Snowy Owls). The story quickly spread via Facebook, prompting a petition and phone campaign to stop the carnage (three owls had already been shotgunned by the PA’s euphemistically named “wildlife specialists” after five others struck planes).

Usually such efforts take days, weeks, or months to bear fruit, and some never do, but by Monday evening the PA had come around and agreed to stop slaughtering the owls and cooperate with trapping and relocation. The outrage from the public, including the birding community, was so swift and so fierce that it overcame bureaucratic inertia.

Every day on social media we see calls to action in support of one good cause or another or against the latest outrage. It’s good to know that raising our voices and signing our names can make a difference.

“Never doubt that a small group of thoughtful, committed citizens can change the world; indeed, it’s the only thing that ever has.”  — Margaret Mead

Rethinking winter hummingbirds

This post is adapted from an article that originally appeared in 2010 in my “Out the Window” column in WildBird magazine. Though the focus is vagrant hummingbirds of migratory species, many of the issues apply equally to semi-migratory hummingbirds such as Anna’s that have expanded their range into areas where winter survival depends on feeders. 

Anna's Hummingbirds are the most cold-tolerant of any North American species, but even they can't survive extended periods of subfreezing weather without help from their human hosts.

A hungry male Anna’s Hummingbird fills his crop moments after a thick layer of fresh snow was brushed off the feeder. Anna’s are the most cold-tolerant of all North American hummingbirds, but even they can’t survive extended periods of subfreezing weather without help from their human hosts.

For more than 20 years I’ve been telling people that it takes more than a bottle of sugar water to keep a healthy hummingbird on the breeding grounds when its instincts tell it to head south. Though that’s still true, it doesn’t apply to the increasing numbers of vagrant hummingbirds whose instincts lead them not to the tropics or the relatively mild southern and coastal parts of the U.S. but to cold latitudes where their chances of long-term survival are slim.

In some cases, these seemingly lost and doomed migrants do make it through the winter with a little help from their human friends, even surviving to return the following fall. It’s the less fortunate ones and the dilemmas they pose for their hosts and admirers that caused me to rethink my longstanding advice to leave hummingbird feeders up in fall.

The vast majority of wild birds live and die without a single human ever taking a personal interest in their welfare, but hummingbirds aren’t most birds. Their deceptive daintiness and apparent dependence on our gardens and feeders trigger much stronger and more complex emotions in us. Small wonder, then, that firestorms of controversy often erupt over whether, when, and how to help vagrant hummingbirds that are struggling to cope with brutal northern winters.

Unfortunately, there’s no one-size-fits-all approach to dealing with tiny birds in trouble. A hands-off policy, as heartless as it may seem, would be the logical choice if wintering hummingbirds were getting by entirely on natural resources. Once artificial feeders and the people who tend them enter the picture, “letting nature take its course” is no longer an option. It’s not so easy to talk about natural selection when you have to look that hummingbird in the eye each morning as it huddles on its slushy feeder.

Intervention has its own hazards, even when left to licensed experts (as required by federal law). The “Three Rs”— Rescue, Rehabilitate, and Release—may fail if delayed until the bird is too weak to survive the stress of capture or if the specialized care it needs is unavailable. Some wildlife rescue groups are reluctant to take in hummingbirds because they don’t have the expertise or resources to provide proper care.

New problems arise when the rescuers decide to add a fourth “R”: Relocate. It was once common practice to capture vagrant hummingbirds, even those in no obvious distress, and fly or drive them hundreds of miles to warmer climes. As we learned more about hummingbird migration, we realized that in most cases this is a spectacularly bad idea. Like many other birds, hummingbirds learn the particulars of their migration routes by experience. Without that experience, a bird that manages to survive capture and relocation may end up permanently disoriented. Release at or near the original rescue site allows the bird to reorient itself to familiar landmarks in preparation for the next leg of its journey, whether further south or back towards its breeding grounds.

When to release a rescued hummingbird can be just as important as where, especially for early-migrating species such as Rufous and Allen’s. Their northward migration along the Pacific Coast is well underway in January and February, when much of the U.S. is still in the grip of winter. Releasing a hummingbird in the dead of winter isn’t as crazy as it may sound. Some of the tougher species have been observed to hang on through blizzards and ice storms only to move on once the weather cleared.

This Pine Warbler is no better adapted to winter weather than most hummingbirds, but few people would advocate capturing it for relocation or incarceration in a zoo.

This Pine Warbler is no better adapted to winter weather than most hummingbirds, but few people would advocate capturing it for relocation or permanent captivity.

Another misguided approach is to sentence “defective” hummingbirds to life in captivity. Though modern zoo ethics discourage taking wildlife out of the wild, this was exactly what happened to a Green-breasted Mango that found its way to southern Wisconsin in the autumn of 2007. This spectacular bird, only the second member of its mainly tropical species ever seen north of southern Texas, was preemptively rescued ahead of a winter storm and transported to a wildlife rehabilitation center. Against the advice of numerous hummingbird experts, center officials decided to turn the bird over to the Brookfield Zoo in Chicago. Members of the hummingbird community lobbied for the bird’s release either back in Wisconsin or in the lower Rio Grande Valley of Texas, but zoo officials were determined to add this avian celebrity to the collection. The following fall a late-migrating Ruby-throated from Michigan ended up at the same zoo under similar circumstances, again against the advice of experts.

How do we keep hummingbirds out of these predicaments in the first place? One simple change in your feeder routine could make a huge difference. Switching to a sugar-water ratio of 1:3 by early September, when high-risk birds may be passing through, will help your visitors put on fat more efficiently while still providing essential water. The higher sugar content also lowers the solution’s freezing temperature without making it too syrupy for hummingbirds to drink, so it’s the perfect recipe for winter feeding as well. Most hummingbirds take to the sweeter solution right away, but you can gradually increase the sugar content over several days to avoid alienating your regular clientele.

Of course, the ultimate solution to the problem is to stop feeding hummingbirds before winter sets in. If you live north of USDA Plant Hardiness Zone 7a  (average minimum winter temperatures 5 to 10̊ F.) and would prefer not to take on the responsibility of hosting a wintering hummingbird, simply take down your feeders within a week after before the first frost or by mid-October, whichever is earlier, even if there are still hummingbirds around. You’ll still be providing a boost to tardy migrants without encouraging any wayward travelers to consider your yard as a possible winter refuge.

* With increasingly erratic weather resulting from global warming, some areas with long, cold winters are experiencing first frosts later in the fall, after most hummingbirds have reached their winter destinations. Taking feeders down while natural resources are still abundant provides a less abrupt transition for any lingering birds and may increase their chances of survival, at least in the short term. [updated 11/30/16]

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Search of the Week: “can hummingbirds drink water heated by the sun”

Rufous/Allen's hummingbird at feeder

A young Rufous/Allen’s hummingbird drinking on a hot summer afternoon.

Of course they can, as long as it’s not straight out of a solar water heater.

But don’t take my word for it when you can easily prove it to yourself. Leave your hummingbird feeder in full sun for a few hours on a hot summer day, then check the temperature of the sugar water.

Unless you’ve hung your feeder near a highly reflective surface and/or inside an enclosed greenhouse-like space, the liquid won’t be much warmer than the surrounding air. This is because a relatively small small volume of liquid in an uninsulated container loses heat to the surrounding air about as fast as it gains it.

Hummingbirds are not delicate, fragile creatures. If the feeder solution isn’t hot enough to damage human skin, it’s not going to burn their tongues.

Addendum, June 23, 2014: A complete answer to this question involves numbers, and I finally got around to getting some on a hot afternoon here in the high desert of southern Arizona:

  • Air temperature in full sun: 95° F. (35° C.)*
  • Feeder solution temperature in full sun: 105° F. (40.6° C.)*

For comparison:

  • Hummingbird body temperature: ~104° F. (~40° C.)
  • Highest air temperature ever recorded in the U.S.: 134° F (56.7° C).
  • Optimum hot beverage temperature: 136° F (57.8° C).
  • Water hot enough to cause third-degree burns to human skin in 5 seconds: 140° F. (60° C.)
  • McDonald’s coffee, pre-lawsuit: 180–190° F. (82–88° C.)

* Air and sugar water temperature measured with a cooking thermometer in my yard at around 2 p.m.; the feeder is a fancy HummZinger with a translucent top, which probably adds a little greenhouse effect to the direct solar heating.

References:

LiveScience: What’s the highest temperature ever recorded in the U.S.?

Brown F., and K.R. Diller. 2008. Calculating the optimum temperature for serving hot beverages. Burns Aug;34(5):648-54. Link (PubMed)

Wikipedia: Liebeck v. McDonald’s Restaurants

The Burn Foundation: Safety Facts on Scald Burns

Search of the Week: “can hummingbirds survive 100 degree heat?”

Costa's Hummingbird

Costa’s Hummingbirds are true desert dwellers, but all North American hummingbirds can tolerate summer heat if they have plenty of water.

Yes. They’ve been doing it for millions of years. As long as they’ve got shelter from the sun and plenty of water for evaporative cooling, they should be fine.

Hummingbirds will drink plain water when conditions are particularly hot and dry and/or nectar is hard to come by, but the usual sources of water pose risks of disease transmission from other birds, poisoning from rain or irrigation runoff contaminated with pesticides, weed killers, oil, antifreeze, etc. It’s safer to put out a separate feeder filled with plain water or change the sugar-to-water ratio of your feeder solution.

When the daytime highs start creeping into the 90s F., I reduce the concentration of my solution to 1 part sugar to 4 parts water. When temperatures rise to over 100° F. (which they don’t very often here in the high desert), I back off to 1:5. In parts of the Southwest where temperatures are topping 110° F., a 1:6 ratio would be advisable. Weaker solutions tend to spoil faster, but on the plus side they also tend to be less attractive to bees.

Providing water for the outside of the bird is another way to help beat the heat. I added a mister to our drip irrigation system that runs for a few minutes a day, spraying into the foliage over my hummingbird garden. It’s used year round but is especially appreciated in summer, helping to keep the birds cool and their insulating plumage in top condition.

I hate to end on a down note, but the hard fact is that every organism on Earth is going to have to adapt to rising average temperatures and greater extremes, and those that aren’t well suited to withstand “the new normal” just won’t survive.

Reference:

Hiebert, S.M. and W.A. Calder III. 1986. The osmoregulatory consequences of nectarivory and frugivory in hummingbirds and other species. Proc. XIX Internat. Ornith. Cong ., Ottawa, Canada.

Related post:

Feeder Solution Evolution Part I: The basics