 'Hirsch' also happens to be the German name for the red deer. Photo by hehaden on flickr.com (CC BY-NC 2.0).  The h-index was proposed in 2005 by physicist Jorge E. Hirsch as a way to measure the productivity and impact of individual scientists. By way of background: Scientific publications frequently cite previous works to acknowledge their contributions. The number of citations a particular work has received is a rough measure of the work's importance and impact. Measuring the impact of individual scientists is a little trickier. We could just count how many papers they have published. But what if most of these papers contribute very little to scientific progress? Alternatively, we could add up the total number of citations across all publications. But what if the scientist just got lucky and was involved in a single high-impact publication with thousands of citations? The h-index deals with these issues by taking both the number of publications and their individual impacts into account. It's defined like this: An scientist's h-index is the biggest number h such that the scientist has published at least h works, each of which has been cited at least h times. What does this have to do with birding? Like many big listers, I keep track of how many birds I've seen in each country I've visited. I thought it would be fun to keep track of the global scope of my birding. Here we face a very similar problem to the one Hirsch solved: What's a good measure of global birding effort? Just counting the countries I've birded in neglects the effort expended in each country: It's basically just a measure of travel per se. On the other hand, a large life list could have been collected mainly in one country (like Colombia, in which almost 2000 bird species have been sighted!) eBird solves this issue by presenting an individual's 'total region ticks', which equals the sum of the total number of species seen in each region. (Regions are not quite the same as countries, but close: Many overseas territories are classed as separate 'regions'.) But even this measure can be magnified by seeing a large number of species in a small number of regions. You know where we're heading with this: Introducing the birding h-index! It's defined as the largest number h such that you've seen at least h species in each of at least h countries (or regions). If you have eBird, it's easy to calculate your h-index: On the My eBird page, simply order your regions by the length of their life lists. Then scroll down until you find the last region whose index (on the left) is less than or equal to the number of bird species you've seen there. The index of this region is your h-index. For example, in the table shown here:
Initially, of course, your birding h-index is mainly limited by how much you've travelled. It's easy to see 10 or 20 species in basically any region, so h-indices in this range mostly indicate how many regions you've visited (and birded in). But seeing 50 or 100 species in a region usually takes a bit of effort, so h-indices this large (or even larger) capture both how much you've travelled and how much you've birded in the regions you've travelled to. What's your birding h-index?
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