Good question. Here is a set of guidelines for this. See page 135 of the following document:

http://www.nmnh.si.edu/BIRDNET/documents/guidlines/Ch6-Minor_August2010.pdf

For small birds, I do the following quick calculation to determine the maximum number of microliters I can collect in total for an individual in a 14-day period:

(M x 10)*0.8= maximum number of microliters,

where M=species-specific body mass. The 0.8 is to make sure I'm collecting only 80% of the maximum amount (just to be conservative and safe for the individual). Therefore, for a bird with mass = 11g, I could take 88 microliters maximum. If there is any hematoma during the blood collection, I divide this maximum value by half, just to be safe. Of course, it is advisable to use your best judgement when collecting these larger amounts of blood from injured or diseased individuals. Sometimes, collection of blood from these individuals will be necessary, however.

I hope this helps.

Best,

Patrick

Patrick, thank you very much! This information is helpful for me. I became a new fan of Birdnet web page.

Ha! Glad the information was useful and that you're enjoying BIRDNET.

Hi,

normally we would assume to take no more than 5% of total blood volume. Total blood volume of birds is generally estimated at about 10% of body weight or 100 ml/kg. I notice US researchers set the bar slightly higher and take up to 10% of blood volume.

We can sample routinely from the brachial vein by venipuncture taking approximately 100-150ul from a 12g finch, which is easy once you get your hand in. hope this is useful.

A simple rule of thumb is that it's safe to take 1% of the body mass -so similar to the 10% of 10% above.

I've done that in hundreds of birds and never encountered any problems.

Field Manual of Wildlife Diseases General Field Procedures and Diseases of Birds. In this book the authors indicate 1% of the live weight of the bird.

Hi Lubos

1% of the total body weight is generally the maximum recommended volume of blood to be collected. Here's a link to a relevant SOP that covers things in more detail. Select "Collection of blood from wildlife (129kb pdf)".

http://www.environment.sa.gov.au/managing-natural-resources/plants-and-animals/Animal_welfare/policies-for-wildlife-research

Hi Lubos,

Even when I agree that a max volume of 1% of TBW is pretty safe (from a physiological and medical point ot views) I would recommend avoiding "rules of thumb" for blood sampling and apply a more case-to-case, common sense approach. Please take a look at the attached paper by: Voss et al. 2010. A hard look at blood sampling in birds. The Auk 127(3):704–708, 2010

Best regards,

Hi!

I been collecting blood samples from small passerines in Mexico for more than 4 years or so. I usually take a maximum of 10% of the weight of each bird. So, if I have a 10g bird, I take 80-100uL blood. By doing so, I have noticed that it is ok for the birds. Of course, Patrick Kelley's answer is very good and can help to control in a better way the sampling volumes.

Hi Lubos, I think the 1% of the body weight is the maximum to draw at any single time and when you have the weight in grams, that is easy to compute in the field. A 10 gram bird should be able to give up to .1 cc's of blood or a 100 gram bird could give 1cc. That is based on the assumtion that 10% of a bird's body weight is blood and you can safely take 10% of that. That all makes the math easier and should be considered a maximum because some avian physiologists use a range of 7 to 10% of the body weight being blood. Another thing to remember is that one could easily replace the same volume of fluids taken by giving a subcutaneous injection of normal saline or balanced electrolytes drawn from a sterile bag and quickly given in the same syringe that the blood was drawn in.

Dear Julio,

10% volume of TBW in small birds is way too much blood IMHO, even if the right sampling technique is applied (that is rarely the case according with some studies as the one cited/uploaded above). You probably have been killing a lot of birds without noticing it (after releasing them back into the wild). A max of 1% would be much, much better, but as I say before, you have to consider individuals (physiological state, nutritional state, etc) and use common sense after a thorough physical examination, rather than simply applying "rules of thumb". With the current analytical & lab techniques, you rarely need that much blood anyway.

All the best,

A friend is a vet who specialises in avian medicine - he assures me that 30% blood loss for birds is not a major problem. This should be available on many veterinary medicine websites.

I do not suggest that you take anywhere near this but it does show how inexact you can be when aiming to take just a few percent.

Perhaps not surprisingly he has sampled many birds of a huge range of sizes/species, for a vast range of diagnostic and nutritional analysis reasons over the years, and any sample, for anything but legions of different tests, need only be very small.

I suspect Julio meant to say 1% if he is taking 100 microliters from a 10 g bird. Back to Lubos' original statement, I am concerned that the plan is to pool small-volume blood samples for virological and/or serological analyses. Pooling generally reduces the analytical quality of the data. If you are concerned about jeopardizing the well-being of the sampled birds for science, then the best data woudl be to test the birds individually. If sample volume is an issue for the tests being administered, consider diluting the sample in a physiological buffer, like phosphate-buffered saline. An alternative method for collecting a blood sample that might be safer than venipuncture for a small bird is to use a xenodiagnostic approach. This is where an ectoparasite is used to take the blood sample, and then the assay for detecting virus or antibodies is applied to the ectoparasite. We are experimenting with this method using mosquitoes to remove blood for detection of arboviruses and arboviral antibodies. Publications are pending.

The usual spot to take avian blood is one of the major vessels on the underside of the wing - they are VERY easy to find as the area is very sparsely feathered and to sample, and pressing lightly againt a wing bone very quickly stops blood loss after the sample is taken.

It concerns me slightly that what is a medical procedure is being discussed by untrained people based on not much more than hearsay.

@Nicholas, @James, @Manuel. Great points you all raised.

As a field ornithologist studying some aspects of endocrinology of free-living birds, it is important that the birds are affected as little as possible. I too have seen statements from veterinarians stating that 30% blood loss is alright for birds, but most of these veterinarians are working in captive conditions. This may work for captive animals that have access to predictable shelter and are safe from predators or intra- or interspecific aggression. Veterinarian recommendations, in my opinion, are very useful for understanding physiological capabilities under benign conditions, and they do indeed establish a baseline for use in field studies. But field ecologists are interested in organism-environment interactions and seek to minimize effects on survival rates or behavior (as much as possible). Perfect technique for blood collection (even from wing vein punctures) is not a 100% certainty and takes a good bit of practice, especially if the researcher is having to contend with mosquitos, sweat rolling in ones eye, a squirming bird, falling branches, etc. I for one have have birds mobbing me, have been in the path of approaching swarm of army ants, and have had a 2m long limb land next to me...all while collecting blood for hormone analysis. It's possible to ignore such things, but even good technique has its distractions. So, just because you may be able to collect X amount of blood doesn't mean you should!

I know this is obvious to everyone here, but I thought I would voice this perspective nonetheless for future readers.

J Patrick - please read my first post again - in full - and note what I mention about quantities required.

Having sampled blood from birds I can assure you that with good handling technique - VERY easy with small passerines where the body is held upside down in the palm and one wing is fanned with the thumb and index finger, sampling from under the wing is simplicity as the skin is all but bare and the vessels fully exposed.

Blood replacement (with plasma) is fast. HORRENDOUS injuries and huge blood-loss that are common in wild birds, either due to accident ,predator or hunting injury seem not to have marked effect, but I'll refrain from details of experience and observations.

@Dave. Could you clarify you concern? It seems that many individuals here have indeed been trained. Or is this not what you meant?

I have seen "trained" field workers (i.e. veterinarians trained on the usual captive bird species) collect blood from the center of the ulnar wing vein, resulting in large hematoma when they slightly lose a grip. My training (by individuals who have sampled blood from >200 bird species from 42 families and from 8-2000g from all continents) taught me to focus on the cutaneous ulnar wing vein in small passerines, as the relaxation of the pressure by the thumb on the ulnar wing vein will partially collapse this part of the vein over the bone and reduce bleeding (as you alluded to). So, my experience (~80 bird species so far) tells me that the most obvious vein (ulnar wing vein) on the underside of the wing leads to far more problems of hematoma (increased cost for bird health and decreased data for researchers). This, of course, is my experience from the field, so it is a generalization. Case-by-case consideration is the key.

@Lubos,

My past experiences in working with North American passerines was that I took 100ul of blood from the jugular vein of birds that were >= 10 gram weight. However, I sometimes collected less than this for birds between 10 and 15 g due to how stressed they seem, their health, etc. I've done what Nick Komar has mentioned above in terms of adding the blood to a phosphate buffer saline solution. For birds

Hello! Thanks everyone for their opinions.

@Nicholas Komar - Your comment about pooling samples is interesting. I will take it into account when designing research.

@Dave Jones - As veterinarian (training with captive bred birds) and bird ringer I don´t think that taking blood from the ulnar veins is the recommendable technique for sampling of wild birds. The prevalence of haematomas is too high. But, it is advantageous (quick performance, easy access) alternative for sampling birds in captivity and caged birds without the need of intensive flight, migration, hunting etc.

The true is, sometimes only handling may act as sufficient cause for the collapse in birds on the migration.

According to my personal experiences, the occurence of haematomas is many times lower after the sampling from jugular vein .

I agree with Patrick a 100%. The problem with "rules of thumb" such as the one we are discussing here (how much blood to take from a passerine bird) is very simple: Generalizations are not good AT ALL in wildlife science. And the reason is simple: Birds should be seen as individuals, not as simple samples in a population. Every single bird we trap is different in so many ways: its water balance, nutritional, physiological, pathological and phenological (i.e. molting) states to mention just a few. Therefore a case-by-case approach is a must and it is the safest way to work when using invasive tachniques such as blood sampling.

All the best,

A couple more comments on this issue. In my opinioin, jugular venipuncture of small passerine birds is advantageous over brachial venipuncture for several reasons, including ease of the procedure without assistance, less risk of vein collapsing, and less risk of torn veins due to bird movement in the hand and therefore lower risk of hematoma and subsequent infection. I avoid sampling from the wing on small passerines but I suspect that a jumpy bird and a heavy hand could also lead to a broken wing. I also use small needles. Very small needles (e.g. 30g and 28g) can slow down the process (because of slow flow through the needle) and can also lyse cells releasing heme into the plasma, which could cause problems for some applications. 27g works best in my opinion, and is sufficiently small for jugular vein of most birds, even small ones. One important caveat. Make sure the needle of insulin syringes are designed for "subcutaneous use" (SubQ), not "intradermal use". The intradermal needles are blunt-tipped, specifically designed not to pierce a vein. I have seen hematomas produced from jugular venipuncture because the researcher was not aware of this distinction.

@ Nicholas. Brilliant points you raised here in particular the one about using SubQ insulin syringes. It has happened once to me and my students down here and it can be really frustrating when you are in the middle of nowhere with the wrong syringes!

Great discussion!

Very much agree with Komar on the benefits of jugular venipuncture, even in smaller birds. Also, there is no substitute for practice: the results for the first 20 or so are not the best, and it is best to develop the manual skill before working with wild birds. We have collected a lot of blood from captive kestrels (jugular), and have found that they recover fine from even large hematoma and in a week there is usually no evidence of the bleed. I don't recommend these birds for producing good data, but using captive birds might be a way to practice and allow the subject to recover.

As a general rule up to 10% of blood volume can be taken from an animal at any given time but should not be repeated for 3-4 weeks. If multiple blood draws are to be performed over a shorter period of time then 1% of blood volume can be taken at each blood draw but I would recommend not exceeding the 10% total. Total blood volume for an animal is species and individual animal specific. As others have mentioned or alluded to, the actual blood volume will be dependent on many factors, e.g. dehydration status, nutritional condition, breeding vs. non-breeding condition, male vs. female, adult vs. juvenile, etc, etc. A conservative estimate for most animals is that total blood volume in milliliters will be 5-7% of body weight in grams, and for birds I believe the number is typically around 6%, though I have seen estimates from 6% to 10% of body weight and there may be more accurate estimates in the literature. If using a blood volume estimate of 6% body weight in grams that means a 50 g bird will have an estimated total blood volume of 50 x 0.06 = 3 ml. So for a one-off blood collection the MAXIMUM amount one should collect is 10% of the total blood volume or 0.3 ml. As far as best place to draw from, I think that is user and species dependent. Jugular veins are typically the largest most accessible vessel for blood draws, but in larger species (e.g. waterfowl) leg veins may be more easily accessible and are plenty large enough. Keep in mind that in any field collection situation animals will be very stressed which may increase the possibility of adverse reactions. I have seen (and confirmed) passerines die from blood loss following jugular venipuncture, hematoma, and handling stress. In addition to acute reactions such as hematomas, capture myopathy and delayed effects of hypovolemia (e.g. kidney damage) are adverse reactions one should consider as well. Attempts to alleviate stress at the time of capture, during captivity, and during blood collection, coupled with decreasing the amount of time birds are held captive should be considered.