--- a/browser/components/migration/MigrationUtils.jsm
+++ b/browser/components/migration/MigrationUtils.jsm
@@ -44,50 +44,16 @@ function getMigrationBundle() {
   if (!gMigrationBundle) {
     gMigrationBundle = Services.strings.createBundle(
      "chrome://browser/locale/migration/migration.properties");
   }
   return gMigrationBundle;
 }
 
 /**
- * Figure out what is the default browser, and if there is a migrator
- * for it, return that migrator's internal name.
- * For the time being, the "internal name" of a migrator is its contract-id
- * trailer (e.g. ie for @mozilla.org/profile/migrator;1?app=browser&type=ie),
- * but it will soon be exposed properly.
- */
-function getMigratorKeyForDefaultBrowser() {
-  // Canary uses the same description as Chrome so we can't distinguish them.
-  const APP_DESC_TO_KEY = {
-    "Internet Explorer":                 "ie",
-    "Safari":                            "safari",
-    "Firefox":                           "firefox",
-    "Google Chrome":                     "chrome",  // Windows, Linux
-    "Chrome":                            "chrome",  // OS X
-    "Chromium":                          "chromium", // Windows, OS X
-    "Chromium Web Browser":              "chromium", // Linux
-    "360\u5b89\u5168\u6d4f\u89c8\u5668": "360se",
-  };
-
-  let browserDesc = "";
-  try {
-    let browserDesc =
-      Cc["@mozilla.org/uriloader/external-protocol-service;1"].
-      getService(Ci.nsIExternalProtocolService).
-      getApplicationDescription("http");
-    return APP_DESC_TO_KEY[browserDesc] || "";
-  }
-  catch(ex) {
-    Cu.reportError("Could not detect default browser: " + ex);
-  }
-  return "";
-}
-
-/**
  * Shared prototype for migrators, implementing nsIBrowserProfileMigrator.
  *
  * To implement a migrator:
  * 1. Import this module.
  * 2. Create the prototype for the migrator, extending MigratorPrototype.
  *    Namely: MosaicMigrator.prototype = Object.create(MigratorPrototype);
  * 3. Set classDescription, contractID and classID for your migrator, and set
  *    NSGetFactory appropriately.
@@ -516,16 +482,50 @@ this.MigrationUtils = Object.freeze({
       this._migrators.set(aKey, migrator);
     }
 
     try {
       return migrator && migrator.sourceExists ? migrator : null;
     } catch (ex) { Cu.reportError(ex); return null }
   },
 
+  /**
+   * Figure out what is the default browser, and if there is a migrator
+   * for it, return that migrator's internal name.
+   * For the time being, the "internal name" of a migrator is its contract-id
+   * trailer (e.g. ie for @mozilla.org/profile/migrator;1?app=browser&type=ie),
+   * but it will soon be exposed properly.
+   */
+  getMigratorKeyForDefaultBrowser() {
+    // Canary uses the same description as Chrome so we can't distinguish them.
+    const APP_DESC_TO_KEY = {
+      "Internet Explorer":                 "ie",
+      "Safari":                            "safari",
+      "Firefox":                           "firefox",
+      "Google Chrome":                     "chrome",  // Windows, Linux
+      "Chrome":                            "chrome",  // OS X
+      "Chromium":                          "chromium", // Windows, OS X
+      "Chromium Web Browser":              "chromium", // Linux
+      "360\u5b89\u5168\u6d4f\u89c8\u5668": "360se",
+    };
+
+    let browserDesc = "";
+    try {
+      let browserDesc =
+        Cc["@mozilla.org/uriloader/external-protocol-service;1"].
+        getService(Ci.nsIExternalProtocolService).
+        getApplicationDescription("http");
+      return APP_DESC_TO_KEY[browserDesc] || "";
+    }
+    catch(ex) {
+      Cu.reportError("Could not detect default browser: " + ex);
+    }
+    return "";
+  },
+
   // Whether or not we're in the process of startup migration
   get isStartupMigration() {
     return gProfileStartup != null;
   },
 
   /**
    * In the case of startup migration, this is set to the nsIProfileStartup
    * instance passed to ProfileMigrator's migrate.
@@ -656,17 +656,17 @@ this.MigrationUtils = Object.freeze({
         this.finishMigration();
         throw new Error("startMigration was asked to open auto-migrate from " +
                         "a non-existent source: " + aMigratorKey);
       }
       migratorKey = aMigratorKey;
       skipSourcePage = true;
     }
     else {
-      let defaultBrowserKey = getMigratorKeyForDefaultBrowser();
+      let defaultBrowserKey = this.getMigratorKeyForDefaultBrowser();
       if (defaultBrowserKey) {
         migrator = this.getMigrator(defaultBrowserKey);
         if (migrator)
           migratorKey = defaultBrowserKey;
       }
     }
 
     if (!migrator) {

--- a/browser/components/migration/content/migration.js
+++ b/browser/components/migration/content/migration.js
@@ -29,16 +29,17 @@ var MigrationWizard = {
     os.addObserver(this, "Migration:ItemError", false);
     os.addObserver(this, "Migration:Ended", false);
 
     this._wiz = document.documentElement;
 
     let args = window.arguments;
     let entryPointId = args[0] || MigrationUtils.MIGRATION_ENTRYPOINT_UNKNOWN;
     Services.telemetry.getHistogramById("FX_MIGRATION_ENTRY_POINT").add(entryPointId);
+    this.isInitialMigration = entryPointId == MigrationUtils.MIGRATION_ENTRYPOINT_FIRSTRUN;
 
     if (args.length > 1) {
       this._source = args[1];
       this._migrator = args[2] instanceof kIMig ?  args[2] : null;
       this._autoMigrate = args[3].QueryInterface(kIPStartup);
       this._skipImportSourcePage = args[4];
       if (this._migrator && args[5]) {
         let sourceProfiles = this._migrator.sourceProfiles;
@@ -80,31 +81,42 @@ var MigrationWizard = {
       document.getElementById("closeSourceBrowser").style.visibility = visibility;
     }
     this._wiz.canRewind = false;
 
     var selectedMigrator = null;
 
     // Figure out what source apps are are available to import from:
     var group = document.getElementById("importSourceGroup");
+    var availableMigratorCount = 0;
     for (var i = 0; i < group.childNodes.length; ++i) {
       var migratorKey = group.childNodes[i].id;
       if (migratorKey != "nothing") {
         var migrator = MigrationUtils.getMigrator(migratorKey);
         if (migrator) {
           // Save this as the first selectable item, if we don't already have
           // one, or if it is the migrator that was passed to us.
           if (!selectedMigrator || this._source == migratorKey)
             selectedMigrator = group.childNodes[i];
+          availableMigratorCount++;
         } else {
           // Hide this option
           group.childNodes[i].hidden = true;
         }
       }
     }
+    if (this.isInitialMigration) {
+      Services.telemetry.getHistogramById("FX_STARTUP_MIGRATION_BROWSER_COUNT")
+        .add(availableMigratorCount);
+      let defaultBrowser = MigrationUtils.getMigratorKeyForDefaultBrowser();
+      // This will record 0 for unknown default browser IDs.
+      defaultBrowser = MigrationUtils.getSourceIdForTelemetry(defaultBrowser);
+      Services.telemetry.getHistogramById("FX_STARTUP_MIGRATION_EXISTING_DEFAULT_BROWSER")
+        .add(defaultBrowser);
+    }
 
     group.addEventListener("command", toggleCloseBrowserWarning);
 
     if (selectedMigrator) {
       group.selectedItem = selectedMigrator;
       toggleCloseBrowserWarning();
     } else {
       // We didn't find a migrator, notify the user

--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -4400,16 +4400,34 @@
   },
   "FX_MIGRATION_HOMEPAGE_IMPORTED": {
     "expires_in_version": "49",
     "kind": "boolean",
     "keyed": true,
     "releaseChannelCollection": "opt-out",
     "description": "Whether the homepage was imported during browser migration. Only available on release builds during firstrun."
   },
+  "FX_STARTUP_MIGRATION_BROWSER_COUNT": {
+    "bug_numbers": [1275114],
+    "alert_emails": ["gijs@mozilla.com"],
+    "expires_in_version": "53",
+    "kind": "enumerated",
+    "n_values": 15,
+    "releaseChannelCollection": "opt-out",
+    "description": "Number of browsers from which the user could migrate on initial profile migration. Only available on release builds during firstrun."
+  },
+  "FX_STARTUP_MIGRATION_EXISTING_DEFAULT_BROWSER": {
+    "bug_numbers": [1275114],
+    "alert_emails": ["gijs@mozilla.com"],
+    "expires_in_version": "53",
+    "kind": "enumerated",
+    "n_values": 15,
+    "releaseChannelCollection": "opt-out",
+    "description": "The browser that was the default on the initial profile migration. The values correspond to the internal browser ID (see MigrationUtils.jsm)"
+  },
   "INPUT_EVENT_RESPONSE_MS": {
     "alert_emails": ["perf-telemetry-alerts@mozilla.com"],
     "bug_numbers": [1235908],
     "expires_in_version": "never",
     "kind": "exponential",
     "high": 10000,
     "n_buckets": 50,
     "description": "Time (ms) from the Input event being created to the end of it being handled"